It's true that missing with an off-hand sword @skill level 210 (ok, 215 with Suppa) does decrease the TP fed to a mob, if you compare with "not missing" with a Sirocco Kukri. Other ideas to reduce TP fed would be full timing hecatomb and/or wield a staff or another weapon that THF has 0 skill in. Or use Subtle Blow gear, maybe.
As for DPS, well, Perdu Hanger may seem to have higher DPS than Sirocco (11.73 with latent active vs 10.4 on sirocco), but this doesn't count the extra wind damage on Sirocco and the very large attack and accuracy difference caused by the 50+ missing skills of dagger vs sword on Thief.
Thanks Snoopie, because DoT matters and keeping track of the TP you feed to other monsters is important as a thief, which most don't seem to figure out since items like sirocco are sorely sought after.