Did Fallout Tactics have multiplayer? Can't remember right now, but if it does, I think it would be great for you. Although, the RPG elements are quite limited there.
It does have multiplayer, and its original cd-case says "Online co-op" in the features list, but there is no co-op (it was cut because the game ended up being rushed, I think), only deathmatch, capture the flag and assault. Maybe there was some sort of "collect batteries" mode as well, but I only ever played deathmatch.