Davelozzi said:
Where is he getting scores like that at 18th level? One power up every four levels means four power ups by this point. Assuming he started out max (18) in both scores, and put 2 in Str, that leaves 2 for Dex, a score of 20 in each.
Don't forget the +5 inherent and +6 enhancement bonuses from the oodles of magic items an 18th level character would probably have.