LOL!
Ay! The game says you are destined to be the most powerful Bhaalspawn, but it seems as though you have to pull every trick you know out of your sleeve and then some. A dash of cheese, some abuse of AI, etc... ... If you try playing 'fair' when you are soloing, you will most likely end up
dead before you even get to touch Jon Irenicus.
That said, my solo Sorcerer had a 'fun' time with Melissan. Using my series of tactics involving Project Image, I had a unlimited source of spells.
PI + Wish = No need to rest anymore!
PI + Skeleton Warriors and Planetars = Unlimited number of summons.
The Melissan Fight