But seriously, only if you have full duration recup and slice and dice rolling with 5 combo points and a full energy bar and are being trained and not setting up a kidney bomb should you be using rupture.
Like everything in PvP, I'd assume it depends on what is going on and what you have against you. I personally always throw it on another Rogue in open world PvP and battlegrounds. The bastards often die when they Vanish and Sprint away.