So if you dual this one at lvl 21 (last level possible with ToB cap) and equip with RingofGaxx and Amulet of Power and Staff or th Magi he gets 99% MR, once/day immune to timestop, invisible, protected from evil, immune to poison, immune to lvl drain, immune to hold, immune to charm/confusion, Grandmastery in Staff of Magi,...
I'm sure this is NOT an overpowered character as he has not 100% MR (although that could be covered with a robe or drow armor.)