So, generally, my point is - don't give up on the arena! I know it's sorta like a demo for early access, but it is a very succesful idea, I love it.
And I personally see nice future to it, if done properly. IMO, you should make more heroes and/or make it possible to create your own builds, but I guess creating more preset heroes is easier to balance out.
It literally has the potential of something like DotA. Only need some ratings, matchmaking, and maybe some visuals aka dress-items as in that same DotA. The gameplay is already fluid, fun, and packs some adrenaline. And it's addictive as hell.
So, devs, please, develop the arena further pretty please