In my experience wipes seem to occur because of:
70% Tank/Healer/DPS combination too weak - either the tank can't take the damage or the healer can't heal fast enough to survive long enough for the groups dps to take the mob out, usually it only takes one of them to make a great group.
20% Bad pulls - puller pulls too many and instead of eating his/her mistake brings it back to group or notices it too late.
10% True IdJet in the group - IdJet (definition) an individual who gets really stupid really fast.
I view dying as part of the game and it usually makes me want to get back in there take revenge. However, the current trend seems to be, if you wipe bail on the group. This is particularly egregious when the toon bailing is the cleric.
Having played a Pally as my main until OoW came out who's nickname amongst my usual weekend group was Mr. Agro, I can attest that a properly played knight will hold agro no matter what even if there are several IdJets in your group who are deliberately trying to grab agro. Once I saw several Wars pulling back mobs before they got to their intended cloth caster (just like my Pally) I realized it was time to look for a new career.