Also happened to me. Played with a very toxic 3-man group, constantly crap-talking us other two, just “for fun”, because the run was smooth and we didn’t die on anything. Kicked both of us when the last boss was at 20%. Didn’t get any XP from the dungeon, got a deserter de-buff. When I messaged a GM, he basically told me that he can’t do anything and I should find another way of leveling if this bothers me, which I think is just unacceptable, but eh. Some people are just a-holes.
I definitely think that this should be punishable in same way, at least when they do it more than once. This is abusing the kick system, griefing other people, wasting their time and overall just being a-holes for no reason.