What level were you? Ba'al is level 30, so I assume you were at least in the high twenties.
When I took him out (level 34) he always dropped unique class equipment, but there may be a level requirement (ie the merchant in High Hall only starts carrying legendary quality equipment once you reach about level 30).
I was planning on taking Ba'al out earlier in my next game, but that could end up being counter productive, assuming that isn't changed too much in DKS.
