I highly doubt the warrior dojo is possible, I attempted it with a very stacked level 200 paladin, both with perf ST and flame sword+shield and it was not even close to being possible.
I think it's possible but very very hard. Completing it once is very doable, twice in a roll needs a lot of luck, but 3 times is near impossible. I'm looking forward to attempting it when my hero's level is a bit higher
I think only dark knights may be able to do it, because you can get 500 hp every 4 seconds from the beholder. Still would be very hard.