Those DoTs Vigilance throws out isn't useless. It may be low damage, but it is of some use in Warzones. Hit the guys trying to get the Objective in Voidstar or Alderaan. Unless they get Cured, they'll be unable to secure that door or console for a bit.
I've tried both specs at 50. Vigilance is far more survivable than Focus, and Focus' burst can be crippling. Focus is a one-trick pony, but it's a helluva pony. Vigilance is flexible and can provide sustained single-target damage.
Burst is king in PvP, but pressure is the queen.
As Vigilance you can keep up decent damage even in Soresu Form, which I find myself in most of the time. But my focus, as it were, is on "tanking" and overwatch so I don't care much about my damage (with only 622 Expertise).