He's in everything not under immediate guardian control. The fallen tech areas of earth, the weapons defense structure of Mars....
I'd believe he's part of the reason the vex haven't advanced further. I see no reason they couldn't just bounce back after the traveler without some other form of attack against them, and Rasputin has apparently been active against the darkness.
He's so interesting though, and there's jack shit known about him! The Vex can make freaking playgrounds that bend our laws of space and time, but they can't simulate a warmind. This should be noticed by more people. He should have a bigger role than what he was given.