I can only speak for myself, but speaking for the average content in the game..

I've only been irritated at healers if someone dies. I've been impressed by healers that pump out damage and no one dies, but never irritated for not doing that.

I've only been irritated at tanks if they aren't holding agro, I've been impressed by tanks stance dancing and doing damage while holding agro and not dying, but never irritated for not doing that.

I've only been irritated at dps if they aren't killing things in a timely manner. I'm happy when they use their utility properly, but usually not irritated. (Unless healer needs mana, bard pls)

My point being, there's doing your job, and then there's being optimal. We shouldn't expect everyone to be optimal, but we should ask them to do their jobs. If they are optimal, commend them! Otherwise, people just let do their job?

P.s. Savage Raiding is another story.