Currently, Arena enemies seem to be assigned by points earned, and what happens is that low-level players cannot fight in the Arena fairly, because most of the assigned enemies are always level 100, with excellent toons while you still have 2 or 3-star toons.

I think a better distribution would be to match people with similar level (levels 1-10 with levels 1-10, levels 11-20 with similar level foes and so on). Now I am level 72 and it's getting fair every day, even though people with level 100 is still very difficult to beat, but at the beginning I was suffering to find a match that I could win.