We must be playing different games.Sigh. No, most of the time they don't. Why are threads like this always ridden with exaggeration?
"As a tank, you always need to know the perfect route!" - no, you don't.
"One mistake and people instantly leave!" - no, in most situations they don't.
Sure, it sometimes happens (though more often than not there's an underyling cause, like overall DPS being low, which will of course create all kinds of problems, or DPS not accustomed with the kick mechanic, which will prolly make the healer leave, etc. etc.). But if there's at least a modicum of skill in the group and you don't die on the very first pull, people will stay after an odd wipe. It's really not that complex of a situation. Group's doing good, mobs fall over quickly, but we wiped due to an odd mistake? We continue. Damage is low, DPS forgot to bind kicks? Yeah, I can see the group falling apart after a wipe - but the wipe is not the actual problem.
Players, generally, are not THAT dumb; they know when they can succeed and when it's going to be a painful experience. If it's the latter, you can't blame them.