Something you could do for rogue, assassin, shadowdancer, and Barbarian, or just Rogue, is give them the PnP ability that they were not given for some reason, that Dwarven defender was; Improved Uncanny Dodge, named Defensive Awareness II for Defender.
In PnP from 8th level on for a rogue and 5th for assassin/barbarian/shadowdancer gains Improved Uncanny Dodge, which more than bonuses on saves versus traps now gives them an immunity to flanking, the only real way to sneak attack a rogue and a powerful bonus all its own, unless the person doing the flanking has 4 more rogue levels than the target. For some reason Bioware did not give this ability to either of those four classes but did implement it for Dwarven defender.
In PnP any class who had Uncanny Dodge via one source and picked up a second class with the same automatically upgraded it to the improved version.
The only caveat about the ability is that its NWN implementation, I believe, gives straight immunity to flanking and does not have any sort of code for suddenly turning on flanking for someone being attacked by a rogue 4 levels higher.