I typically go a different direction from the frost builds on bowas.
Magic Arrow works alright against the vampires, but honestly the best thing is just to get amp on them. Only two really viable options are Atma's Scarab and Witchwild String.
If I'm you I farm a WWS, socket with ShaelNef, use that with Laying of Hands, make a Lionheart, keep harmony on switch for frw and valk buff. Then spec strafe, use regular attack for PIs that don't break with Amp, and go to town. At that point you can farm pits pretty well.