Thanks for the weapon insight and advice!
At level 13, my finesse Rogue is dual-wielding Fell Rapiers of Ice, has Cutthroat Smallblade, a Sun Blade, and I believe a disruptor and paralyzer. Perhaps I should bank those, switch to Kukri, free up a feat slot by dropping Finesse, and switch Improved Crit over to Slashing. (I also need to drop Toughness for Precision.) Guardian of the Liturgy looks tempting, though; and now I notice it's a slashing dagger! I'm sold!
With Knife Spec, does Improved Crit double the enhancement's +1 crit range? I thought the Improved Crit did its doubling first, and then enhancements added on afterwards; making daggers a 16-20 in this case. Perhaps the way Keen is treated has me confused?
After a TR, I would likely level up with something like this until the effectiveness of TWF kicked in:
http://ddowiki.com/page/Item:Staff_of_Nat_Gann
Back to the Drow build; feats would be Precision, TWF, ITWF, GTWF, IC: Slash, and two undecided feats. Weapon Focus to make Power Critical available? There's probably something better.
Thanks again!