Its been ages when I last touched my BGII cds, but I have soloed a kensai/mage & sorcerer, and I know people that have soloed every thinkable class/dual class..
Don't fight me about tactics/tips, because I haven't played BG2 in like 1,5 year time, what I can say is that your character will ascent to such a high level (due to you get all the experience points you earn) that you will find your character overpowerd in some situations, this was the thing that happend with my kensai/mage soloer ... it was just amazing what a katana wielding mage can do in some situations
