entire ssc/tk except vashj and kaelthas should be expected to be downed without an explanation prior to the attempt simply because every person in the raid should already know exactly what the boss does without even seeing what the boss actually looks like in game.
PvE is just that simple, no-brainer clicks at the correct time which is told to you in the middle of your screen with a boss mod, the rest is simply a gear check.
knowing your class and your gear is required if you want to play WoW, not if you want to raid, so that shouldnt even be mentioned here. telling us you want this/that doesnt help, look up where is your upgrade for you does. I know every single piece of gear upgrade in the game before i was even attuned to karazhan, and i refused to raid when i was simply not geared for it. in my healing set i have over 1500 healing and 146mp/5 with only 1 piece from karazhan, if i can do it, then you can do it.
imo if you want someone to gear you up by carrying you through a raid, that is selfish, not as much for healers, but for a tank, when i die, the raid wipes, it's just something I cannot afford to bring it to the rest of the raid.
Lurker and void reaver are fights called "idiot check", im sorry if that sounds rude, but it is a fact. we should be downing these bosses on a weekly basis using less than a hour for each.
what i see as problems:
1. people don't care about the raid content, but they want to raid(expect others to carry them for the loot).
2. too much downtime; I see TOO many people between trash pulls just stand there doing nothing, then complain about oom when the next trash pull starts, if you are a warlock, life tap, standing there and wait for your mana to regenerate is not an option, this becomes a huge problem in ZA since fights are timed.
3. you don't even know your class. your shot rotations, what's the max dps shot rotation? how do you value hit rating vs crit vs dmg? how do you convert mana/5 into healing? examples: 21/40 ds/sf warlocks need 202 hit rating 30% crit 1k shadow dmg in order to be effective, what's your magic number, do you know? this comes in as a greater problem when it comes to lurker adds. EVERY single class has some utilities to save yourself from dying to an elite mob that hits hard, but do you know how to use it? I can tell you to put pet stay then MD the guardian to the pet thats far away from you will shake the guardian off of you long enough for a cc/tank, but the highest lvl hunter i have is lvl 14, knowledge about your class? more like common sense there. if you don't know something, ask and learn.