Hearthpwn

With such minor cosmetic additions at $9.99 each they seem incredibly overpriced. Knowing my OCD if I got 1 I'd probably end up getting the rest if they were more reasonably priced. I'll probably hold off for awhile unless they go down or are offered in some kind of discounted bundle pack like in HoTS. Even if they are "optional" I don't see how getting all 3 Alternate heroes should cost more than a single full expansion. 

Any alternatives to Fel Reaver? I disenchanted mine awhile back.

In my opinion:

Neutral - Harrison Jones > Alexstrasza > The Black Knight

Class - Tirion Fordring > Grommash Hellscream > Mal'Ganis > Neptulon

If you want to play Control Warrior you really want both Grommash Hellscream and Alexstrasza together. Of the two you'd want Grom first and Alex 2nd. You can getaway with just Grom in the Patron Warrior variation, but without Alex Control Warrior won't function nearly as well. Alex is still pretty niche and only really seen in Control Warrior and Freeze Mage, although there is more potential for other decks with Dragon synergy.

As for Harrison Jones and The Black Knight they are more situational. If you have the spare dust I'd definitely recommend crafting them so you can adjust to the meta as need be, but they just aren't auto includes in most decks and can be replaced with other viable 5/6 drops like Loatheb, Sylvanas Windrunner, and Emperor Thaurissan pretty easily.

For class cards I have to say Tirion Fordring is by far one of the strongest and most valuable legendaries in the game and a must have if you like to play Paladin. Mal'Ganis is good and now that Demonlock has become more popular I think he's worth crafting if you want a change of pace from Zoo/Handlock. Neptulon I generally wouldn't recommend given that Shaman's aren't very popular and they have enough RNG as it is. I crafted him along with Al'akir for Midrange Shaman awhile back and almost never play it with so many other more viable decks. It's not that he's bad, I think theres just better cards to spend your dust on unless you are a dedicated Shaman player.

If you must cut something I'd say Kel'Thuzad. Typically most Druid decks only run 1 of big 3 (Cenarius/Ragnaros the Firelord/Kel'Thuzad) and KT fits more into control I think. Right now it seems to be taking the place of where Azure Drake would be which is okay if you don't find yourself needing the extra card draw/spell power. Otherwise Mind Control Tech or Zombie Chow would work as well, but in the rare instances I get Chow in the early game it's just so valuable I can never get myself to cut it.

If by value you mean the most golden cards produced/related to the best I can think of are:

Dr. Boom + 2 Boom Bot

Onyxia + board of Whelp

Lord Jaraxxus + Blood Fury + Infernal

Tirion Fordring + Ashbringer

While I like the idea of a no Legendary mode similar to the MTG Pauper format (only common cards) it wouldn't be profitable for Blizzard to implement that mode. Collecting high end cards is the bread and butter of any CCG. Without them there would be far less incentive for people to spend hundreds or even thousands buying pack after pack. If all we needed were Commons, Rares and even Epics it would be far easier to get everything you need with a much smaller investment of money and/or time grinding Arena. Legendaries also allow for more complex decks with their typically more powerful stats and unique abilities which can be essential to certain archetypes. You can try playing without them or use budget alternatives, but it generally won't allow for the same type of gameplay and will make things less fun. It does put newer players or those unwilling to invest lots of time/money at a disadvantage as it severely limits what kind of decks you can use without many of the core legendaries. I think things are fine as they are (for now), but something will need to be done eventually or it will turn off newer players trying to get into the game as more and more cards are introduced.

If you're running combo Druid you'll need the 2nd Force of Nature, but you can make due with 1 until you get everything else you need crafted first. Druid relies mostly on its class cards so make the 2x Keeper of the Grove and 1-2x Druid of the Claw if you're still missing them. Since you already have 2x Ancient of Lore the only other Epic you need to craft is the 1x Big Game Hunter and the rest (besides legendaries) should be easy to get. As for Piloted Sky Golem its an above average 6 drop that is more of a filler outside of Mech decks. I wouldn't recommend it unless you are missing Sylvanas Windrunner or Emperor Thaurissan to take its spot.

Dr. Boom is a must have and should be one of the first Legendaries you craft. As for the other essential Neutral Legendaries I'd say get Ragnaros the Firelord or Sylvanas Windrunner followed by the situational Harrison Jones and The Black Knight. I'd hold off on Ysera until the rest of BRM comes out and maybe Dragons will become more popular.

If you want to invest into Druid Cenarius is a consistent and reliable late game option. Stat wise he's kind of expensive, but is out of Big Game Hunter range which is a plus. I rarely end up using the +2/+2 option although the double 2/2 Taunt has saved me many times. If you prefer to be more aggressive he can just as easily be replaced by Ragnaros the Firelord if you don't mind the RNG. In my opinion they are equally good in their own way so it mostly comes down to personal preference.

http://www.hearthstonetopdecks.com/

There are a few different variations as of today. It's still early in the season so there may be minor changes as we try and find the most optimal spot for Emperor Thaurissan.

Depending on how the dragon synergy works out it could raise the popularity of Ysera and Alexstrasza. I'm hoping that Emperor Thaurissan can open the door for Malygos in some kind of super burn deck, but that just seems unrealistic.

If you're trying to work with what you have I'd say you're closest to making Demonlock/Handlock with Lord Jaraxxus and Mal'Ganis. You already have most of the essential neutral legends Dr. Boom/Sylvanas Windrunner/Ragnaros the Firelord so you have some options. You'll still need all the necessary Epics, but you can try Ramp Druid, Midrange Hunter, Control Mage or Oil Rogue as they don't require anymore legendaries. I don't play much of Priest, but if you can make due without Vol'jin Control Priest could work. In Midrange Shaman you can substitute Al'Akir the Windlord for Doomhammer. The only classes I'd rule out would probably be Control Warrior (no Grommash Hellscream+Alexstrasza and Midrange Paladin (no Tirion Fordring) which are incredible important. You can always try budget substitutions, but the non-aggro decks are usually the ones that rely on the Epics/Legendaries the most. 

Naxx has a good amount of staple cards so I'd definitely recommend getting wings #4 The Construct Quarter and #5 Frostwyrm Lair. The most noteworthy cards being:

The Construct Quarter - Zombie Chow/Mad Scientist/Death's Bite/Dark Cultist

Frostwyrm Lair - Echoing Ooze/Shade of Naxxramas/Kel'Thuzad 

I don't think #3 The Military Quarter is necessary unless you need Spectral Knight or Voidcaller but thats up to you.

The problem with (Grommash Hellscream + Alexstrasza) and (Lord Jaraxxus + Mal'Ganis) is that they pigeonhole you into specific archetypes. I'd say get all the essential Neutral Legendaries (Dr. Boom/Ragnaros the Firelord/Sylvanas Windrunner) you're missing first as they get more value across different classes.

Control Warrior requires the most Epics/Legendaries to work properly so I'd only recommend getting Grommash Hellscream and Alexstrasza if you have most of the others already. Alexstrasza is still good in Freeze Mage as well and may become more popular if Dragon decks actually become a thing.

If you like playing a more midrange Warlock (not zoo) I'd definitely recommend getting Lord Jaraxxus as its one of the best class Legendaries in the game. Handlock doesn't require Mal'Ganis to function, but you still need the Giants which can be expensive to craft if you don't have them yet. Demonlock requires both Legendaries and you'll only see play out of Mal'Ganis as long as it remains the flavor of the month. Unless you are adamant on playing Demons , I'd say wait a little bit and see how the meta turns out first before making him.

How does it compare to Harvest Golem and Spider Tank? I don't see 5/2 being chosen very often so it's basically a 2/5 for 3 mana most of the time which isn't particularly good or bad. If Transform really can't be silenced back to a 2/2, a 2/5 (stat wise) seems stronger than Harvest Golem although not as sticky. I would have personally preferred: "Choose One - Transform into a 4/3 minion; or a 3/4 minion" to get out Priest range. That would have been better than Spider Tank which has decent stats, but loses out to Shade of Naxxramas in the long game. Shade is good and all, but given the lack of viable 3 drops I'm really hoping for some more diversity.

How often does anyone choose Charge over +2 Health & Taunt? I've gotten Charge to work a few times for lethal or to setup lethal, but 99% of the time Taunt just seems like the overall better choice. Am I missing out on some hidden combo/tactic or is this the case for others as well?