The rule of the thumb is - if you feel uncomfortable and annoyed too much to enjoy the game or even to be able to concentrate on performing the tasks of your class - leave. I always try to communicate fist, both to ask for help or advice if I'm unsure of the strategy or it's a new dungeon for me as well as offer help and advice to others but once I see an arrogant approach from someone and obvious uncooperativnes I consider leaving. I've actually so far only left ones as the group (at mid-range dungeon) was absolutelly incoherent, not waiting for buffs after wiping on the first boss anr in general running around as headless chickens with zero communication. Couple more other times I've left after some other players rage-quit midway through the dungeon and there was obviously no chance of continuing anymore due to the time running out etc.