Obliterate is 10 meters, and it does not interrupt - only immobilize.
As for "no such thing as ranged advantage" - yes there is, and it can be capitalized upon. There's also positional advantage, which I fully execute when running my Sniper (MM), Gunslinger (Engi\Engi hybrid) and Sage (bubblestun hybrid) in PvP. There are also some Ops fights that are distinctly more ranged-friendly than melee-friendly.
It's not black and white. Far from it.
no just no there is no ranged in this game.