Alright, let's with long way.
If in raid i see, how other healer hardly heal (even when it's not needed (yeah, hello scripted fights)) i just gonna full damage. Because why not? For overheal, so my MP gonna flew off with other healer MP? Btw, almost all battles can be solohealed.
About dungeons you already saw my message. Soo, what new? There is no toxicity at all.