Alrighty folks, just got done with the fourth wing of Blackrock Mountain...it took longer then the first 3 and boy was it frustrating
Much like Naxxramas (for those who completed it) the bosses in this wing were a lot more RNG dependant, especially Chromaggus and Nefarian.
So let's get on with it:
SPOILERS:
Razorgore (Heroic): The main issue with this boss is keeping his eggs (0/3) under control, specifically not letting them reach 5 health and hatching into a 7/7 Chromatic dragon. If you can manage the eggs, this fight isn't very difficult.
I used a Priest deck. Silences and Mass Dispel are great to stop his eggs. Mind-control tech and Cabal shadow priests are great to steal his eggs. Don't forget SW:P and SW just in case. I found Light of the Naruu helpful as well.
Try and get some 3-attack minions on the board to instantly get rid of new eggs and dmg any eggs that you can't kill to stall them from hatching.
*BEWARE* - make sure and keep decent board control because he does cast bloodlust and can ruin your day!
Vaelastrasz (Heroic): His hero power makes you both draw 3 cards every turn and he uses Naturalize so he can easily start milling you. I was able to defeat him using a Druid Murloc deck. Low cost minions are essential, you can flood the board and prevent yourself from getting milled.
I also used Naturalize to Mill the boss and kill any big minions he plays. Poison seeds/Starfall combo is great here as well. Since I was running poison seeds, any deathrattle minions that summon another minion was great to maintain board control.
He uses Gang-up, I found you just need some luck so he doesn't use it on anything too annoying.
This fight will take several tries due to RNG, but he's not too bad!!
Chromaggus: Okay...here is where you need your lucky rabbit's foot and make sure you ate your lucky charms, RNG is king here. The most important thing for this fight is to make sure to get rid of the spells he gives you with his hero power every turn: specifically the one that deals 3-dmg to you every turn, and the two that reduce the cost of his minions and spells...the ones that heal him and duplicate his cards are of less importance at the start.
I used a Priest deck. Important cards to have in your deck are, Lightwell for heals, Mogu'shen Warden and Deathlord. The whole strategy here is to maintain as much board control as possible until you can drop one of the taunt minions and do a Divine spirit/Inner fire combo. If you can manage to get a lightwell on turn 2, all the better.
Once you can pull off that combo, do everything you can to keep that minion alive: heals, light of the naruu and circle of healing are great. Once you gain board control and have your buffed taunt minion, start discarding the spell that heals him and go for face.
*BEWARE* - save silences and SW:P for his Chromatic mutations, or if you can prioritize killing them outright.
This strategy took me over a dozen attempts and a lot of luck. So good luck to you!!
Nefarian: Another boss that needs a lot of RNG and numerous attempts. Since he gets 10-mana by turn 2, he can easily overwhelm you with his dragon minions.
The key here is Paladin. Humility and Aldor Peacekeeper will keep some of his high attack minions in check. Try and save your Equality/Consecration combos for when he's got a full board. Zombie Chow and abusive sergeant will help keep board control, as will Mind-control tech and Sylvanas. Since he does pretty much start with full mana, he will burn through a lot of cards. The key is to get a board clear when he's got only a few cards left, this is when you can deal with whatever he plays while building a board.
I also ran with 2x holy lights and 2x guardian of kings to keep my hp up, I found them necessary because you will take dmg prior to getting board control.
Again, this will take a lot of tries and some luck...don't get discouraged!!
Besides the heroic bosses, the class challenges were decently fun. It was sort of designed as a way to let you try Demon Warlock which is something Blizzard seems to be aiming for the lock. The Rogue challenge was cool also, lots of gang-ups and no minions in your deck (I didn't get any anyways).
I hope my strategies helped you win in this wing. I'd love to hear if you came up with some other decks to beat these bosses!!!
Have fun and good luck.