Diablo is and always has been a pve game, why are some people so up in arms about trying to make pvp work, go play a game that's more suited to it. Diablo is balanced from the perspective of classes vs creatures, not classes vs each other, that would require a literal rebuild of the game from the ground up to make work competitively.
PvP will come back, you are right it will need to be re-introduced for the aspect.
But I think it will be a selling point of the next D3 expansion.
Regardless, D3 will always be mainly PvE