I very often help other players.

Since I'm boxing five, I mostly stopped helping horde though. It happened few times that I killed a poor guy unwillingly. Like click on the horde player to see his level, decide that he is not a threat, move on to next mob, forget to give the system enough time to accommodate target lag, send pets in ... Oops, 4 gorillas on the poor Undead mage ... So I prefer to just ignore them most of the time.

Just like when I was single and dual boxing, I never attack first. I don't see the point of killing one character using five equivalent level ones. Well, I don't attack first unless the player made it into my KOS list, that is.