The question is: When does outlining a novel work?
Personally, I have to have a sense of what my story is and where it's going. If you're writing a mystery like me, then you know you have to have a good idea who the crime solver and killer are and who wins in the end.
Of course, having a not-so-normal killer can be difficult. Take my novel for example. I had to have a good grasp on the ending, because, well, my killer can't exactly have handcuffs thrown on him. Nor can he live it up with a bunch of jailmates.
Yeah, that's why I needed a solid outline for this one(though I'm always up for revising it). In order to make something believable to others, I have to believe it myself. And, I can't do that if the ending doesn't flow and become feasible.
The one thing I ALWAYS do, however, is the whole character sketching. Not right away, anyway. Then, I write a sample chapter where I let the characters interact, and generally, I am able to figure out their personalities from there and build on it.
That's just me though.