How could you not do LK at least on normal mode? I mean come on level 80s are soloing him and a full raid couldnt kill him? Hardmode I buy as I never got my kill until 4.1 and even then took a few attempts. That fight is no joke but its really just a retard check. If you do everything fine and you have people that listen and pay attention its easy. Or you get herpderps defiling the raid, or not killing frost orbs and half the raid goes "wheeee" off the edge, or a tank that doesnt turn the raging spirits and they silence everyone... and its painful and then they are the ones that "always go WTF this is a level 80 raid you guys suck". Then you check recount and they have 10k DPS and no damage done to Valks even though they grabbed all the healers. Or someone always doesnt make it off the platform. Or people refuse to move away from shadow traps and you see half the raid go "wheeeee" off the platform.
I would say Heroic Sindy was more of a pain. Frost block 20 people....sure why not. HM putricide was also a pain as were Princes but only on 25M on 10 those were easy.