Hearthpwn

i am using this card in Mechrogue deck and it works pretty well even when u cant build vol7ron .. i use 1x Conceal in my deck so i get the voltron combo unless enemy aoe my ass to the ground.. it works pretty damn good esp in rogue deck coz u can colblood him and u dont just get 4 more dmg u get 4x4 =16 more dmg which is insane.. vol7ron proved valuable for me in my handlock matches where i finish enemy warlock at 16 hp with it... the other thing about mimiron's head is that even if u dont conceal it enemy players just want to kill it asap this turn so they waste some removal or even sacrifice board control to do it which is also good thing.. i like the card and pulling off the combo as rogue wasnt as hard as it is with other classes (i can imagine sort of freeze-mech mage can also pull it off pretty well) ... but there is something major about mimiron's head which u cant miss -> dont sacrifice very important mechs.. once i sacrificed shredder+sensei+mimiron and it wasnt worth it in the end coz my enemy pulled out a sludge belcher => i didnt get lethal -> he dealt with voltron after... so try to use him when u know for sure you got lethal or when u are going to sacrifice very bad mechs for him .. training dummies are probably best friends of mimiron coz u can pull the combo 90% of the time for 6 mana as rogue ..

edit: also take this into consideration when playing mimiron's head you want as many spare parts as possible + being rogue really makes it alot better.. Shadowstepping a voltron means that it will cost 6 mana on next turn and it has charge + mega windfury with 8 hp
spare parts -> amazing combo with him.. +1 attack spare part means +4 total dmg, reverse spare part means u got 8/4 charge mega windfury - 32 dmg unbuffed... and ofcourse the stealth and return to hand spare parts make voltron usable 2 turns in a row which means WIN in 80% of the games

Witness this combo happen against me and it was badass.  I had this card but disenchanted it for rares as I don't play a lot of mechs anyway.  Kinda regretting the disenchant as I want to see for myself if I can pull it off but oh well.  This sacrifice made me win naxxramas heroic.  

Forming V-07-TR-0N (VOLTRON) on game is hard but I pulled one out rather easy on BRM first mission with a similar deck than this one:

It's too hard to pull off, and if you do you are most likely already winning. Even then - I am not sure it's such a great investment for something that could potentially die to removal or be neutered by silence.