I've never been vote kicked because of bad performance, I just find myself kicked when DC'ed - even if it's just 1 minute at the start of the instance -.^
Sometimes even when I mention that I quickly have to reboot due to my gfx card playing up, they prefer kicking me then waiting a whole minute.
I was kicked from a Well of Eternity group when I was healing once.. I had never wiped on Mannoroth before that. Apparently nobody was killing the two Dreadlord Debilitators that pop up after you kill Captain Varo'then, and I didn't notice at first. I mentioned that we needed to kill them (after dying to the endless adds). I didn't get mad, or blame anyone, I just said they needed to be killed, and they kicked me. They probably thought I was supposed to be able to heal through endless spawning adds that weren't being killed while they tried in vain to slowly dps down Mannoroth. Ever since then I have always remembered to take matters into my own hands and go over and moonfire (or smite, on my priest) the dreadlords to death myself.
That's the only time I can recall being kicked. I am usually quiet, and try to be polite in groups.
So far I've only been vote kicked once... it was in halls of origination and I was doing the quest with Brann so I had to wait for him before I could turn in the quest and hop on the elevator. I told them in party chat and then bam was removed from the group. Other than that I do try very hard to play my classes to their potential so it's not an issue.