I have completed the first arena matches and damn, that was a challenge. Not the enemies or the debuffs, no, not at all. The fighting was easy, but I think, I simply lack the endurance to fight 5 round with 5 waves over and over again. It's simply boring. 
Afterwards I reached match 4, 5 and 6. Yeah... I'm definitely not gonna play 20 rounds with 5 waves each now. No thank you!
Maybe it's fun with friends, but alone its just tormenting.

(2/5)

This is the worst DLC of all times. It's a really long series of several arena battles and it's really hard to beat it. You don't earn XP,  you almost don't earn any loot, and if you die you have to restart the whole arena. How it should be fun at all?