It actually does dunges faster then I could most of the time, and I don't think it's ever failed a dung on me, if it has it's more because my character I used it on sucked dick and died a lot. It just depends on your levels, on a shitty 1 def pure with 40 att and 40 str I was hitting about 4k XP p/h in F2P at 40 dungeon. Obviously you'll do a lot better then that at 60 P2P and assuming you're using it on a much better account.
You should be getting similar XP rates you would be doing solo on your own without botting, it really is that fast. I'm sure if you look on their forums there's people posting their xp rates. It's probably one of the most impressive scripts I've used, I just don't like using powerbot.