Temperance axe is better than having a ridill (on BST, same for war if they could use? don't know), so long as you have enough stones to keep it swinging, simply due to the higher skill. I think had war been able to use it, we'd never see temperance up and alive.
This thing is just sex for a bst, I was tanking due to the amount of swings I was doing, it's really nice. You have to see it in action to understand it. It procs as many times as joyeuse does, and everyone here knows how awesome the TP gain is with a Joy or Ridill. Imagine you had that in axe form
Now the question if it's worth keeping in offhand or not : Considering the fact you'll double attack frequently with it, your DoT will probably be the same, if not, more than you using a higher dmg axe, because it'll let you rampage things faces more frequently. Like I said before, the amount of swings I was doing combined with WS'ing, made the mob fight me. I must have been doing something right ey?