Arena would be nice, but I feel like there would be solid metas on what is considered a good setup, and you'll be forced into that meta if you want to join a team. Or you'll be doing it with friends, and likely wont win against that meta, since it's the meta for a reason.

For example, I can see a meta right now being Astro/Warrior/Summoner only. Deathflare destroys Drk's (Insta kills them through walking dead, which is probably a bug) and just about everyone in general. Warriors are as OP as it gets with double/triple Fell Cleaves, Holmgang, self healing for sustainability through healer CC's, and just their all around high survivability in any situation. And then Astros are just the ultimate run and gun healer, and are the hardest healer to take down at the moment.

Problem is, is these things will likely stay, excluding the death flare with walking dead thing. SE doesn't seem to have much of a focus on PvP to keep it balanced the way a ranked Arena or ladder match setup would require. Though it'd be cool if they were there.