My personal experience with Arena on AoB is only with 0.9.9.6, when Arena was on either Floor 2 or 3.
If Arena appeared on Floor 2, restart.
If Arena appeared on Floor 3, attempt. I usually make it past the first wave, and then the second wave kills me because berserker loves to proc when nothing is around to berserk on. Argh.
On another note though, I had a Blademaster Sunrise Iron Fist + Conqueror run on ITYTD earlier where I finished Arena with 3 levels into Brute instead of getting Berserker, since from prior experience, Berserker probably would not proc at the times I wanted it to proc (see definition: RNG). In a similar situation, I wonder if a point into Hellrunner or Tough as Nails would have been useful, but I doubt one extra point of armor would help as much as some more dodge chance.