Definitely a solid champion.  Currently the most common place I see Arix is as a go 2nd nuker in arena.  2 turn Stoneskin with an AOE A1 and a self Counter Attacker is very powerful.  Combine that with the constant turn meter boosting and healing and he can be very annoying to take down.

He's not bad. Multipliers are pretty good, especially on the A2 - 0.35x HP, compared to, say 0.44x HP for Magnarr, which is lower, but Arix has higher base HP, which helps compensate, especially when you include the fact that Arix's version stuns, as well as not requiring the condition for the second hit.

Personally I don't use him, but if you're a newer account I definitely could see him having value.

i pulled him from a shard a while back, i did get him to 60, he has some uses in arena, im not sure i would call him a nuker but more so for cc, i put mine in a stun set and he helped me get through 21 fw and i use him occasionally in arena battles and in some hard DT floors if im going all in with cc.

I've seen Arix used in high high live Arena and Tag, but you'll need to check out Shini's Arena videos on her for more about that build and how good she actually was.