As a note, the Expert is supposed to be a bit weaker in combat... he's got all class skills, so he does everything else better. But with that said, Iajuitsu Focus + Blurstriking Gnomish Quickrazors can do a very significant amount of damage, and using UMD to turn into a Dwarf Ancestor can really help out your AC (you have to be an outsider for the latter to work, otherwise Crucian is the best you can do). And Imperious Command + Intimidate + the armor in Drow of the Underdark that lets you intimidate as a move action is quite nice. If you can manage to go first (+1 Eager Armor Spikes of Warning?) and get to him fast enough to keep him cowering, he'll never act... which means he's flat footed permanently. Just make sure your Intimidate skill is high enough (Item Familiar?).
JaronK