It wasn't balanced, no; But arena -- in a larger picture of things along with increased design focus on funneling people into raids and 'raids' (lfr) -- was responsible for the way classes were reduced to what we see today, with a landslide of other consequences from 'item squishing' to 'pruning'.
There's little nuance to arenas, leading to dull class design. And if you're claiming 'skill', well... No. It's been debunked numerous times in the thread, chain-cc and pillars isn't skill. It isn't fun, either. And if all you have to say for why you disagree is 'well u suck get gud' -- I don't think you're winning this argument. And it's not like arenas are going away. All I want is for duels / larger-scale pvp to feel less like a messy afterthought. And unfortunately 'balancing around 3v3' is not entirely compatible with that.