How are dungeons/raids in Wotlk ?

I have playing wow for a very long time (Played through TBC, Wotlk, Cata, Mop and Wod) but Wotlk is the one expansion where I never had the opportunity to do high level content and I'm trying to change that now , thanks to this server.
I'm a big fan of hard raids and complex dungeons so I was wondering how hard the raids in Wotlk are. I sometimes hear they were easy and faceroll but I'm still asking to be sure.

I'd like to know if :
- End game raids have good mechanics that punish bad players (standing in fire etc...)
- Can Casters/Melee DPS (Ret pallies/Enhance)/Healers go OOM during a fight ? (I feel like it's literally impossible to go OOM in Mop/Wod)
- Can hybrids be expected to offtank/offheal if the tank die/healer is OOM or it's generally not worthwile (or healer never go oom)

Wotlk is relativly hard.

-Standing in fire will mostlikely kill you in seconds.
-1 mistake can cost a whole raid wipe.
- Most of the classes without proper gear and proper playing will go oom easily.
- Hybrids can't do much in raids.