Hmm you are right. I forget about "max 4 players in game".
Clans are good to gather friends together and improve BN society.
I think about creating area where are only heroes and places to PvP.
But also it's true if someone want to have PvP he can just enter "diablo 3 realm" and fight with other player where monsters are.
Hmm PvP for 4 players?
Max 2v2. That's kinda small group :/
That's why I think about something like close arena (small to decrease latency) where can enter more than 4 players.
Clan Wars (CW) would be better in arena, where you know where you will fight and you can't run away using TP. Also increased numper of players would let to create better synergy between characters than in teams where is max 2 players.