Using logic, I would believe what Architect says.
Just another proof that Nihilus fancy little "drain power" is completely ridiculous and does not at all fit in Star Wars. Why don't we have a Professor X that can kill every living being at will with just that machine of his?
Now suppose, we only know what Kotor II did tell us. Were we told that Nihilus' drain is uncounterable (yes I know that little cutscene with Kreia.. but what does Kreia know? it worked on her, wow, big deal)?
Why should that power be uncounterable? Who sais Revan, who knows a lot more about the force than Kreia, does not know how to counter it?
Well it is all speculation.. but don't believe Nihilus would wipe the floor with Revan.