The most interesting man in the world has this advice on careers:
"Find out what it is in life you don't do well... and then don't do that thing."
As a Warcraft player, we don't want anyone thinking that you're doing the very thing in your WoW life that you don't actually, well, do well. Well well well. To explain my point, I have included this handy chart of the very essence of each role and what it should do well:
So yes, if you can't do those things well, you should probably not do those things. A tank holding aggro on only 1 mob out of a trash pull, a healer selectively letting people die, and a dps being alt-tabbed while the dungeon is cleared... not cool. Don't do that thing.
But suppose you have the general idea of your role down pat. You keep mobs on you as a protection paladin. You keep most of your party mostly alive through a dungeon run. You do good dps and things are dying. Should you be happy? Should you just bask in a half-assed type of glory?
You've probably guessed that the answer is "NO!"
Here are some tips of what everybody from tank to healers, through dps and even rogues, should think about when doing dungeons. This applies to people still gearing alts right now before Pandaria launches and it applies to veterans who have server first titles who will be leveling to 90 in less than a week's time. To situate this post, I've recently gone from 75 to 85 as a Paladin tank (Equinok on Moon Guard - US) entirely from random dungeon groups.
-Makes sure to buff appropriately.
-Don't attack something before the tank has hit it.
-If you can interrupt, interrupt everything!
-If a skull is marked by someone, kill the damn skull.
Pandaria delenda est