[geo981010]

Not every LQ is destined for Wither Bones greatness - the D4 ones with a Skull Staff will only get about ~20 fatigue per casting total, so try it with them. A D3 + staff one is about ~30, so they are ok, but if only D2 they should find another job - Astrals can Nether Dart (maybe communion if you have some lizards about and go for WB), Bloods should be hunting for slaves, and of course my Favorites the Natures should be casting Relief. Two casting relief means even the D3 LQs are able to cast it several times.

As for accuracy particularly with LQs, try an Eagle Eye casting first. The attack LQ flavours (Nether Darting and Wither Boning ones in particular) should have that scripting first. It helps for Vine Arrows too!