Well, with the memories of that plot returning, I think I got an answer for my own question.

Spoiler Alert, click show to read: 
The difference between your void in the force and everyone elses (aka all the baddies) is basically that you're not killing things. And a dead force in a living world is what Kreia wants (might be obvious but the thought haven't fully occured until now). Darth Nihilus slowly drains everything to death and that force draining skill kills the exposed.

But were the exile "fail" is that while you drain force energy, you don't consume it, or to but it otherwise: You're a black whole that instead of sucking the force in (while leaving everyone alive) you keep all that force stuck around you and transfer it to those around you through your bonds.

Kreia tries to make that you automatically expands that hole. thus killing the force, but fails.