Baane is a ridiculously overpowered boss, and I'm at a loss for how to solo him.
I'm level 129, I'm using the highest possible tier of the Witch Hunter's Bundle Gear, minus the Vampire Squirrel pet.
I have all Death spells except the Scion of Death and the craftable/card pack spells plus Epic, Aegis & Indemnity, Virulence, Brace, Shadow Shrike, Tower Shield, Weakness, Stun Block and Reshuffle.
I would suspect the problem is your gear. That witch hunter gear is just ugh. The wand is good, but the rest is only good for stitching. If you don't have a good pet you probably are rocking around 15% resist. I have little trouble soloing, but my gear has like 60% resist and 120+ damage. I advise you try to get Darkmoor gear from Malistaire the Undying in the Graveyard dungeon. That will easily carry you to 130 where you can get Dragoon gear, which is very strong. You can also farm Corporal Tenni'syn for the Baleful Light Brigade armor, which is also very good and on par with the Darkmoor robe.