As there has been said just put a dmg reduce to stop the 1 shot fest, that could happen.
New items, maybe even Runewords that allow people to come up with ways to mitigate the damage, that could happen. Remember this: Ah there comes the full pve set glowing barb/soso and BLAM! he's down, 1 shotted the poor bastard.
What I'm worried is the 4 player cap, that's not something that is easy to rise, or is it? But hey, maybe they have that whole arena thing in back pocket just waiting for right moment.
For the fun of it I will test PVP next weekend I'll rather stay optimistic.