EDIT: Added the mulligan guide!
Hey guys, I just reached legend yesterday with my take on Mech Mage and wanted to share it with you! Proof of legend:
The list itself is pretty close to what the "classic" Mech Mage used to look like, but there are still some notable changes I made that I think are relevant to make the deck viable in the current meta, so I will focus on explaining those changes since the rest should be common knowledge already.
Why no Fel Reaver?
Fel Reaver is a high risk-reward card that can close out games extremely fast, but also backfire very hard. In my opinion it has it's best use in a hyper aggressive version of the deck, while my take is more focused on consistency (in terms of risks and synergies). Knowing that, if Fel Reaver is what you're looking for, try out the Tempostorm version: https://tempostorm.com/hearthstone/decks/countess-aggroreaver-mech-mage.
Why do you not run Mad Scientist and Mirror Entity?
For the most part I just wanted to make the deck more consistant in what it's doing, which is getting board control early on and then snowball from there using mech synergies (Tinkertown Technician, Goblin Blastmage). While Scientist into secret is arguably one of the most powerful tempo plays in the game, there are also some downsides to it; In an aggressive meta, it's pretty easy for your opponents to play around mirror entity with small 1-drop minions, also you get no mech synergie off of it which makes it less likely to get your synergies consistantly.
Why do you run Acidic Swamp Ooze when you already have 2 Snowchugger?
Because the meta is pretty weapon-heavy, and Snowchugger alone often times just doesn't do the trick. Against Patron Warrior it's way too important to have an answer for his Deathbite setup in time.
Why 2 Harvest Golems over 2 Spider Tanks?
Pretty much the same reason why Ooze is in the deck, the meta is pretty weapon-heavy, Spidertank just dies to Deathbite / Truesilver Champion often times and you loose massive tempo and mech synergie on board. One Spider Tank is still needed though because your curve can get really awkward otherwise.
Why the Flamecannon, isn't that a Tempomage card?
Because a lot of relevant meta minions are at 4 health (Armorsmith, Flamewaker, Leokk/Misha, Azure Drake...) and it allows you to keep your minions at full health instead of having to trade them off.
Is Manawhyrm really worth it? There don't seem to be a lot of spells to go with it.
Manawhyrm in this deck, unlike tempomage, only has the purpose to get on the board as soon as possible and trade off your opponent's early game minions so you can play Mech Warper / Clockwork Gnome and your other mechs uncontested. Don't get greedy with it, just use it to make 1-2 good trades to make space.
If I have any tech cards I want to use, which cards shall I take out for them?
I was changing quite a few cards over the course of the last week, trying out different builds and there is definitely room to make changes depending on which matchups you want to focus on. If you want to put in tech cards you can switch out Ooze, Manawhyrm, Flamecannon or 1 Tinkertown Technician.
I don't have Dr Boom and/or Archmage Antonidas, what can I replace them with?
Either Piloted Sky Golem or Ragnaros should do the trick best.
Mulligan guide + some gameplay advice:
Note that I will only focus on the most common matchups in this guide to keep it somewhat short and not tl;dr, so if you got any questions about how to mulligan in any matchups I will not mention here let me know in the comments section.
Before I go into the certain matchups, let me talk about the mulligan in general which is quite simple really because it's quite similar in most cases, you pretty much ALWAYS want a 1-drop in your hand or at least a 2-drop when you have coin, it's important to get on the board as soon as possible and snowball from there, that will give you the best chances of winning overall. That beeing said, I will just talk about specific cards you look for in the different matchups.
The mulligan is the same for Zoo and Handlock, look for a good curve (1, 2, 3). If you know for sure that it's Zoo and you're holding the coin, keeping Blastmage in addition to at least a 1-drop is fine as well. If it's handlock, decide on how "ham" you have to go by your hand; if you're holding direct burst spells, try to always hold them back for lethal if possible and try to force a situation where the opponent has to decide whether he want's to heal or taunt up (make sure he can't do both in the same turn) and then 1-shot him with your board dmg (in case he healed up) + your burst spells. If you don't have any direct burst, try to rush him down before he can draw into his keycards and don't play around Moltens at all (even if it sounds stupid).
Snowchugger is really strong in this matchup since it basically denies your opponent the use of his hero power and weapon buffs so definitely mulligan for him, other than that Flamecannon really shines against rogue since there are so many good targets (Drake, all 3-drops, Teacher if you ping her as well). But only mulligan for Flamecannon when you already got some early game minions, that's always your first priotrity!
Similar to Rogue, Snowchugger really shines in this matchup, also Ooze is a fine keep if you already have a 1-drop, if not he's a bit too slow to keep (since your opponent won't play waraxe if you don't give him a target to kill on turn 1). The mulligan is the same for Patron and Control Warrior, and you're working against the clock in both matchups, so curving out well is very important. Against Control Warrior don't be too afraid of Brawl since it will cost his whole turn to cast it often times anyways, keep swarming the board and only hold back on maybe a Clockwork Gnome so you have an activator for mech synergie after he brawled.
Simple mulligan, look for a 1, 2, 3 curve pretty much and that's about it, that goes for Tempo Mage as well as the mirror and Freeze Mages. Also Blastmage is fine keep if you have the coin since it can swing the board very effectively. Against both Tempo Mage and Mech Mage you want to go for board control early game as much as possible, it's very important to denie their combos and synergies while setting up your own Blastmage / Technician.
Considering the fact that most Shaman's nowerdays are Mech Shamans you should mulligan against them, besides the usual early game you should actually keep either Frostbolt or Flamecannon against them because Whirling Zap-O-Matic is just too big of a threat. If you manage to get board once against them you have pretty much won the game anyways (since they don't run Lightning Storm), so a more defensive mulligan is totally fine. if you know for a fact that the opponent is Midrange Shaman (incase it's a rematch for example) just mulligan for 1, 2, 3 instead.
1, 2 curve + removal is what I preferably look for against priest since most versions run Deathlord and you need a way to break them before they spin out of control with Velen's Chosen or Power Word: Shield. Flamecannon usually does the trick best, but frostbolt works as well most of the time (in case you have board as well that is ofc). Besides that, only play around Cabal if you can afford to, playing too slow or scared will only help the priest since he can just recover over time.
Snowchugger is your best friend once again, as well as Blastmage + coin. Against Eboladin it's important to dump your hand quickly, so preferably play 2 1-drops instead of a 2-drop in most cases to not give him good Divine Favor value, besides that go for board control early on as much as you can and keep him frozen if possible. Against midrange only trade if you really need to, it's important to put pressure on them early on because they have a lot of taunts and heal mid-lategame.
Simple 1, 2, 3 mulligan once again, Snowchugger helps as well. Against both Facehunter and Midrange hunter you go for board control first and then start racing them once you got a decent board build up, don't be scared if you fall like 10hp behind in the early game cause they ignore your minions, you can still easylie win the race once you get board!
Very simple (and probably your best) matchup. Just look for a good curve and try to snowball them down, that's about it.