Mandatory mechanics (at least, mandatory as current content).
I was reviewing the combat log from last night, where we wiped 7 times on Maegaererewhatever and then called it. More specifically, the first 3 deaths per wipe (the rest aren't important once you know you're going to lose). While I saw the usual and understandable, such as "Cinders not removed because 8 second dispel cooldowns suck" and "non-Breccia tank had a brain fart and taunted the wrong head", I also saw 4 deaths to "player was insta-killed from 100% health by Acid Rain ground zero" and 3 to "player ran behind the tank and got breathed on". I think I owe the hydra an apology. Clearly we weren't giving it the respect it deserved. And that's really the point. My raid group's going to limp embarrassed into the 20% nerf zone to get past 4/12 N because we're just not trying, and that's our fault, not the monster's.
Don't get feared into the whelps. Don't stack up for Gruul's petrify/shatter. Kill the Lich King's snowballs. Bounce the ball back at Zon'ozz. Somebody interrupt that guy. A fight just isn't memorable if it doesn't have something that you must do, or else you die horribly and it's your own damn fault. High DPS, excessive heals, and unkillable tank (I'm looking at you, DKs) are nice, but winning because you know this s#&^ cold is much more satisfying.