Duelist. Good lord, duelist.
The best I could come up with was Rogue4/Swash3/Duelist7/Invisible Blade5/x1, and ALWAYS, ALWAYS, fighting defensively, so you have an actual AC.
At one point, before I had ToB, I wanted to build a Halfling weilding a dagger in one hand, nothing in the other hand, totally unarmored, who
didn't rely on stealth, and was designed to fight humanoids with class levels instead of MonMan fodder. What I ended up with was Swashbuckler 3 / Fighter 6 / Invisible Blade 5 / Duelist 4 / Monk 2; had 51 AC and saves of 25/30/24. Attack line was +28/+28/+23/+18/+13(1d4+26 +4d6sneak), and only marginally worse in an AMF. That was her primary strategy btw - Torc of AMF, negate most buffs and defenses, and kill them by inches. AC in an AMF was still 32, high enough that most PCs would have trouble without magical support; and she was still getting 27/27/22/etc to attack in the AMF, meaning she could hit just about anyone now that their magical boosts are down. Otherwise, it was all about Feinting as a free action with a +50 Bluff mod.
So yeah, IMO that's the good use of Duelist - getting another source of AC that works inside an AMF, for use against PCs who don't have the ridiculous attack mods that monsters generally seem to.