In short: I feel kinda dissapointed in this dungeon. It’s realy boring to kill waves of mobs and we don’t have bosses encounters. I did it to lvl 140 and left, dunno what after that. No bosses too? I don’t even know why I want to do that. Experience only? Meh.
Stand in middle, run left, run right, circle may be, kill barrels, pick runes/shards/repeat. 
It’s need improvements. For first: boss every 40 encounters to feel progress? Rewards, may be it’s solved with p1.? Some mobs upgrade like in monolith? Anyway, it’s for testing your limits, but boring. I have a ton of keys in stash and can get even more easily, but for what? We have keys reward in monolith, arena keys easily to get. But why? To enter boring dungeon again? I don’t wanna. Did T1-4, lvl 130-140 endless. Thats all. Bye bye arena. May be for loot from t4, thats all. Sigh. Wasted stash place with keys.