I was getting annoyed how people talked about Deck of Lunacy and I finally decided to sit down and think and analyse this through. This will get long but I will try to keep it well formatted.
Let's get some stuff out of the way before I get into the nitty gritty:
I will evaluate how good some cards are regarding how well they do in a vacuum. If a card invokes Galakrond I will only evaluate the part without the invoke. Similarly if there is some synergies in a card that mage can't use, it will get a bad rating.
I will evaluate DoL in a deck that has both minions and spells in it and uses DoL as the last push and final win condition. I'm not arguing if that deck is good or bad as I'm just finding out if DoL is good as a card. I just need to say this as I believe that DoL doesn't work in a spell-only deck.
Most of the cards will be good with the 3 mana discount so I won't address this from this point on. I will, however, remark it if that makes a said card especially good.
I will talk about each mana cost as a category, evaluate the over all category and divide their cards into good, neutral and bad ones. I will highlight some high and low rolls from both extremes. Note that I only talk about spells from 10 to 3 as lower cost spells are just impossible to get. All the situational or purely random cards will be neutral as they can be both good or bad.
All of this will be based on standard including the newest expansion.
All the % will be rounded up after .5 or rounded down under point .5. So 4.6 is 7 and 4.4 is 4.
This whole analysis is also based on that DoL is purely random and doesn't have any hidden leanings towards any other class (like discover had a tendency to give cards form your class).
The cards in the subcategories (good, neutral and bad) are in no particular order. They are in the order I read them from here. You can click the link if you need the cards visible for reference and doing that you can also easily follow my analysis.
I have 3 mana spells in my list but I didn't use them for my analysis as Mage don't have 0 mana spells in standard.
Now that's out of the way, let's get on with it:
10 mana (7 mana after DoL)
All the ten mana cards are good and even better with the discount and there's quite small pool of them. There's Dimensional Ripper, Eye of the Storm, Mind Control, Nagrand Slam, Puzzle Box, Pyroblast and Survival of the Fittest.
Good. Nagrand Slam, Pyroblast and Mind Control. They all either do good damage or clear the board and MC has the added effect of stealing one of their minions to your side.
Neutral. Eye of the Storm, Puzzle Box and Survival of the Fittest. EotS is a good card and you're basically paying the discount as the overload next turn and I think Mage doesn't always have the courtesy to not have 10 mana every turn in the mid to late game. SotF on the other hand is good depending on how many minions you have left as it can be useless or an instant win.
Bad. Dimensional Ripper. I doubt Mage has any good minions to summon from their deck for 7 mana. It might get decent with Khadgar or Vargoth but it's still bad with a big B.
43% chance for good, 43% chance for neutral and 14% chance for bad.
9 mana (6 mana after DoL)
Like with 10 mana, all of the 9 mana spells are decent if not better. What makes them better that there's only 3 in the current rotation. Those being Libram of Hope, Mass Resurrection and Plague of Death.
Good. Libram of Hope and Plague of Death. A good heal with taunt and and an amazing boardclear.
Neutral. Mass Resurrection. The discount is good but resurrect is only as good as your dead pool.
66% chance for good and 34% chance for neutral.
8 mana (5 mana after DoL)
At 8 mana spells are starting to get lower from OP and start to be more situational as there's still spells that are extremely good with the discount but others are still meh as they are starting to work towards deck goals mage doesn't have.
There are 14 spells in this category:
Good. Cenarion Ward, Deep Freeze, Idol of Y'Shaarj, Inner Demon, Lay on Hands, Power of Creation, Tidal Wave and Twisting Nether. These are all cards that either do direct damage, heal you, clear the board or fill your hand. Basically these all tip the board or the game in your favour.
Neutral. Grand Finale and The Forest's Aid. Grand Finale is much better at 5 but requires your deck to have elemental synergy. TFA on the other hand is good... but it's not as good as others. Also 2/2 as a stat is quite easy to clear. TFA early on can be good tho.
Bad. Gift of the Wild, Guardian Animals, Jewel of N'Zoth and Tip the Scales. GotW is just a bad card even for 5 mana and it would need some synergy to go with it and as we talk random, the synergy might not be there. The rest are here for the same reason as Mage doesn't have any support for them to make them useful.
57% chance for good, 14% chance for neutral and 29% chance for bad.
High rolls would be Cenarion Ward, Deep Freeze and Power of Creation as they all tip the board or the game heavily in your direction. High roll chance is 21.4%.
All of the bad cards are low rolls. Low roll chance is 21%.
7 mana (4 mana after DoL)
7 mana spells are either extremely good or horrendously bad with only some situational cards in between.
There are 10 spells in this category:
Good. Earthquake, Flamestrike, Mask of C'Thun, Overflow, Sprint and Soul Mirror. These all either give mana efficient damage or they refill your hand. 4 mana Sprint (that doesn't tutor).
Neutral. Cycle of Hatred, Expendable Performers and Fel Guardians. CoH and EP are both decent boardclears if the need arises but there is better options. I wanted to rate Fel Guardians as bad but there's a good possibility for it being 3 or less mana better Mirror Image, which might save your life in some niche situation. It's still bad but it has enough niche to it.
Bad. Commencement. I just doubt that there's anything in your deck that you would like to pull out as Mage tends to be battlecry heavy.
60% chance for good, 30% chance for Neutral and 10% chance for bad.
Earthquake, Mask of C'Thun or Overflow would be your high rolls depending on if you need boardclear, damage or heal/refill. High roll chance is 30%.
Low roll chance is 10%.
6 mana (3 mana after DoL)
6 mana spells are funny as they are really sub par but they are suddenly good with the discount. Their effects also seem to be more general making the cards overall more valuable. Note that you will get most of your spells from here.
There are 18 spells in this category:
Good. Avenging Wrath, Blizzard, Candle Breath, Hidden Oasis, Nourish, Siphon Soul, Skull of Gul'dan, Unidentified Contract and Unleash the Beast. Most of these are just better versions of other spells in this mana cost and the rest are super cheap card draw (Candle Breath and be 0 mana draw 3!). And then there's Unidentified Contract and Unleash the Beast...
Neutral. Deck of Chaos, Hand of Gul'dan, Initiation, Pharaoh's Blessing, Runic Carvings, Starfire and Swarm of Locusts. Deck of Chaos works in mage as quite many cards are low attack and high mana cost (all of the dragons and most of the legendaries) but it's random so it's not good per say. Hand of Gul'dan is still a good draw but a lesser version of other card draws seen in this mana category. Buff cards require you to have something on board (not always a given) and Runic carvings has a similar reasoning like The Forest's Aid has. Swarm of Locusts is decent but dies easily to AoE and is only really good if your opponent can't clear it or if you use it to clear something.
Bad. Darkest Hour and Starfire. You don't want to summon minions from your deck and you DEFINITELY don't want to destroy your own minions as Mage. Starfire on the other hand is just overshadowed by everything else in both damage and card draw.
50% chance to for good, 39% chance for neutral and 11% chance for bad.
Your highest rolls would be Unleash the Beast, Unidentified Contract, Blizzard and Skull of Gul'dan. High roll chance of 22.2%.
And you really don't want Darkest Hour. Low roll chance of 5.5%.
5 mana (2 mana after DoL)
5 cost spells are far and wide in scale as there are many that are good and many that are niche. I'm putting the emphasis on many as from now on my explanations for cards are getting shorter and I will also divide any further cards into 5 tiers instead of 3.
There's 28 spells in this category:
Good. Blessing of Authoritai, Bloodlust, Brawl, Chaos Nova, Libram of Justice, Malevolent Strike, Metamorphosis and Rolling Fireball. These are all just good and they all happen to be boardclears or otherwise massive board effects.
Eh. Assassinate, Apexis Blast, Command the Illidari, Explosive Shot and Time Rip. Other spells are better and there's some requirements to fill. I would like to rate destroy a minion effects highly but Malevolent Strike is just better (It's 0 mana Assassinate, can't get better than that).
Neutral. Aeroponics, Bane of Doom, Blessed Champion, Cutting Class, Dragon's Pack, Hagatha's Scheme, Plague of Wrath and Starfall. Other spells are better but these are not bad.
Meh. Force of Nature, Glowfly Swarm, Psyche Split and Righteousness. These can be good but usually they are just bad.
Bad. Duel, Holy Wrath and Hunting Party. There's no synergy for any of these.
28.5% chance for good, 18% chance for eh, 28.5% chance for neutral, 14% chance for meh and 11% chance for bad.
High rolls definitely include every spell from the good section. High roll chance of 29%.
Low rolls are the same as bad. Low roll chance of 11%.
4 mana (1 mana after DoL)
4 mana spells are strong in effect but sadly there are also some class specific spells that just don't work on Mage.
There are 44 spells in this category:
Good. Auspicious Spirits, Blessing of Kings, Cascading Disaster, Cone of Cold, Dunk Tank, Equality, Fireball, Hex, Holy Nova, Marked Shot, Polymorph and Ring Toss. These are all extremely good spells for 1 mana and add tremendous value to your play.
Eh. Bite, Conjurer's Calling, Consecration, Hammer of Wrath, Hellfire, Mass Dispel, Mindgames, Molten Breath, Overgrowth, Potion of Illusion, Power Infusion, Shadow Word: Ruin, Swipe, Torrent and Vendetta. These are either lesser versions of good spells or just otherwise not as good but these are still viable and you should be happy if you get these.
Neutral. Germination, Glide, Grave Rune, Mortal Strike, Multi-Shot, Shadow of Death and The Dark Portal. These are either niche or some other spells do their job better.
Meh. Fiendish Rites, Impbalming, Scrap Shot, Shadowflame and Vivid Spores. These are cards than can be good but they are bad as hell or don't have synergy with Mage but you could use Impbalming as a removal... But you shouldn't.
Bad. Blade Flurry, Dr. Boom's Scheme, Soul of the Forest, Soul Split and Unsleeping Soul. Just horrible. Concede if you get these :D
28% chance for good, 34% chance for eh, 16% chance for neutral, 11% chance for meh and 11% chance for bad.
High rolls would be Auspicious Spirits, Dunk Tank, Equality, Fireball, Polymorph and Hex. High roll chance of 14%.
Any bad card is a low roll. Low roll chance of 11%.
As an average out of all this, you will get a good spell 47.5% of the time**, a neutral one 40.2%** of the time and a bad one 12.3% of the time.
Also your average chance of high rolling is 32.23% while your average chance of low rolling, and conceding :D, is 10.36%.
And then some random percentages that might interest you:
8.13% of these spells can deal direct damage to the face and deal quite a lot of that.
18.7% of these spells summon minions without prerequisites.
13% of these spells are boardclears.
8.13% of these spells are minion buffs.
The rest 52.04 is divided between card drawn, single target minion damage effect and random fillers.
There's no duplicates in these statistics and and I didn't count some utterly rubbish spells like Fiendish Rites etc.
This took me more than it should but there you go, the statistics behind Deck of Lunacy and now you can go and decide if the card is viable or not. Random is the word of the day and it is the word that will destroy this card.
But maybe, just maybe, 47.5% is enough...
(I could link all the cards as this is Hearthpwn but I'm not going to. This took quite awhile to do even without that formatting.)
what about 3 mana spells? granted mage has no 0 cost spells (bar shuffling a coin i guess) but priest and rogue do and will probably end up stealing this often
I was going to count them in but then I thought of three things:
Mage doesn't have 0 mana spells in standard
I wanted to only focus on Mage and if they would put the spells in a deck. Randomly generated spells tend to always be somewhat good.
There's 68 standard spells that cost 3 and even more in wild and I was already 3 hours in when I looked through 123 spells for this list.
But I can write you a note I made, "3 mana spells are mostly minor effects that are amazing for 0 mana but most are still quite bad." These spells would certainly be more useful than Priest and Rogue's 0 mana spells in the late game but still they're not quite worth it. I would say the statistic would turn to worse. Something like 20% 40% 40%.