The resisting of Force drain might work in a way that a user pulls drained Force back or simply instills it inside himself. If you pull handreds air balloons (non-Force sensitives), they get along. But, if you try to pull 100kg boulder (Force user of Sidious caliber), than would it move?
Darth Krayt learned Force drain from Nihilus' holocron, which means he could do the same thing as Traya at least. But did it kill Luke and Abeloth within seconds? Luke didn't even notice being drained at first, it took him a while to figure out. Yet, he had enough strength to fight till the end and was the one giving final blow, when Krayt was finished. And even after, while Krayt was in slightly better condition, he still didn't risk engaging Luke.
Too much hype is given to Force drain.
While Kotor 2 didn't have adequat match for Nihilus except Exile, here most of the Sith have enough power, knowledge and experience to resist and fight him.