Hmm... very good points across the board. Thank you to everyone so far.
As dantheman points out, Quick Draw is a prerequisite for Dread Pirate (egads, such a useless feat...), so I'll have to put that in the build, probably as the level 3 feat since I won't be able to take Martial Study before level 10 anyway. Luckily I get Weapon Finesse from Swashbuckler.
The problem is that now I'll have to squeeze another feat in there somewhere or drop a feat, like Improved Initiative, which would in turn mean dropping Nightsong Enforcer and the 1d6 SA that entails. It's not a serious loss, especially since it's made up for by the 2d6 from Assassin's Stance. I definitely don't want to drop Lion Totem Barbarian or HaR Fighter, though.
Fitting a couple levels of Swordsage would allow me to take Cloak of Deception and Assassin's Stance without burning feats, but it would eat into the Swashbuckler and, thereby, cost me another 1d6 SA. On the other hand it would allow me to take that level of Nightsong Enforcer AND be offset by the 2d6 SA from Assassin's Stance. Hmm... decisions decisions.
1 Rogue, TWF and Craven
2 Rogue
3 Rogue, Quick Draw
4 Swashbuckler, +1 Dex
5 Swashbuckler
6 Swashbuckler, Staggering Strike
7 Dread Pirate
8 Dread Pirate, +1 Dex
9 Dread Pirate, Improved TWF
10 Scarlet Corsair, Improved Feint
11 Barbarian (Lion Totem Variant)
12 Fighter (Hit and Run Varian), Daring Outlaw, +1 Int
13 Scarlet Corsair
14 Scarlet Corsair
15 Swordsage, Greater TWF
16 Swordsage, +1 Str
17 Swashbuckler
18 Swashbuckler, Improved Initiative
19 Swashbuckler
20 Nighsong Enforcer, +1 Dex
How's that look? I have an open feat at 12th level with this build, if my numbers are correct. It won't be quite the powerhouse at 12th level, but it will get much more powerful between levels 15 and 20. What do you guys think? Are there other choices that would be more optimal?