I think. In case you didnt find back them, you can buy NWN diamond for 10$ on gog.com. Then you have to ask (by the gog site) for a valid cd keys (sold are duplicated).
You forgot to take critical focus preepic. My version of the blackstaff build is wiz 32 wm 7 bard 1. I will summarized it later but keys are 32 wiz for +6 weapon modifier, bard at level 39 to max tumble/disc /umd, 4-5 point in perform for +1 ab from song, and armor proficiency.
I have noticed a bug if you call blackstaff spell twice, weapon modifier is removed on second call if the first isnt elapsed (if your ab is 55 with 32 wiz level, call blackstaff = 56 ab, call blackstaff = 50 ab).
He has sent two Mordor disjunction on my tank (DD air elemental with 98 ac) then he has level drain him two or three time then he has spamed death spell... lovely....