personally i would not bother, you are going to lose something if you multi class or take a Prc, either bab or spell casting.
possibly m/c with rogue, boosting your reflex save and grabbing evasion? you still lose bab and spell use, but you gain some dice of sneak attack and tumble, which is useful for a lighter armoured warrior type, then you can use arcane channeling in a flanking position and slam them hard!
i think duskblade is a nicely balanced class as it is to be honest though and needs little adding to it.