Back in Wrath, and to some extent BC, I considered it a failure on my part if someone in the group died. Did I use all my CDs? Could I have used BoP or LoH to save that person? Was my game not at 100%? With the healing we had at the end of Wrath, everything was treated with a Holy Light - just in case.
Now? I don't mind if a DPS dies.
Fire is finally bad
Here's a big problem with players now, particularly those that thing Heroics are too hard. Back at the start of Wrath I remember going into H-HoL and taking on Loken. This. Fight. Was. Hard. Move too slow - dead. Don't move in fast enough - dead. Nothing on the planet could have prevented it. I managed to get the achievement on my Shaman long before I did on my Pally, and that's only because we blew Heroism and CH was OP.
H-UP, final boss - the one that dies and comes back as a shadow. Ignore that shockwave at the start of Wrath, and you were a smear on the floor. Hunter in H-OK? You're dead in the first Mind Control. Anyone remember what happened in Vanilla MC when you didn't run out of the raid during Baron Gheddon? Yeah - you wiped the raid.
Of course a year+ into Wrath, and fire was a joke. The only thing on the planet that could kill you was Defile - unless it was a heroic Putricide ball. Even Sindragosa's cold snap was eventually laughed into submission.
Unfortunately this mentality of ignoring mechanics and laughing at damage rolled into Cataclsym dungeons and heroics. Asking someone to CC something is a sign of weakness, and if you do manage to get a CC off odds are someone will break it on the pull. Unfortunately, this attitude will kill parties faster than you can say "Have you ever been to the Deadmines?".
If you've run H-Deadmines successfully, you've probably picked up this achievement - the one that basically laughs at anyone who "doesn't" move out of the fire. What I think is lost on players is that unlike Wrath (or maybe like Wrath - depending on your pov), heroics are finally teaching players how to raid again.
You absolutely cannot afford to overheal - mana just doesn't allow for it.
Standing in the "Giant Big"(TM) will get you killed.
Failing to kill Adds fast enough will get you killed.
One person's failure can wipe the party/raid.
Spending gold on enchants/gems/gear is cool again. Even if it does set you back 3 days worth of grinding.
You cannot walk into an encounter with a random group of people and expect to faceroll your way to victory.
Letting you die
In the end, I still love the Heroic level we have right now. I'm going to feel a little sad if we wind up doing the faceroll dance in another month, but I suppose it could happen.
Oh yeah - if you die because you stood in fire, I'm not going to feel bad about that. I'll just chalk you up as an acceptable loss.