Most of my random duty finders have been only positive experiences, but we did come across one of those guys... a DPS who ran all over the dungeon pulling mobs. I, as a Healer, was young and confused and I followed him, which ended up with both of us dying.

My reaction to this was to apologize to the party. The DPS' reaction was to continue to Leroy Jenkins the dungeon. The other guys tried to tell him it was the tank's call which mobs to pull, which made him reply sourly: "Well. I'll just stop helping, then!"

I have to admit, I was a bit shocked. Never before, or again, have I met a DPS with that kind of attitude.