Marksman is the better choice most of the time.

Virulence is interesting because it has the best defensives and worst offensives of the sniper specs for pvp. 70% slow after roll, 5 second longer ballistic shield, DR after shield probe breaks, etc. are all very useful for staying alive. The problem is you have no burst at all, and cull is heavily LOS dependent so it's easy for your opponents to line. Sins and ops can purge your dots fairly regularly as well. Spreading dots also prevents your team from cc'ing targets (bigger issue in ranked than regs).

Marksman with the Agitating Energies tactical is actually a better version of virulence offensively in pvp, you may want to give that a try if you like the viru playstyle. Refraction point is an excellent aoe cleave tactical, and B-O Targeting is your go-to for burst and mobility.