Rogues are not underperforming in PvP, and are on par with Warriors, Warlocks, Shamans, Mages, and Hunters, according to Holinka:
https://twitter.com/holinka/status/461918081292316672
3s Ladder:
43 Rogues (top is #32)
-------------
214 Shamans (top is #6)
129 Warriors (top is #3)
96 Hunters (top is #16)
85 Mages (top is #2)
81 Warlocks (top is #11)
Compared to potentially underperforming:
84 Priests (top is #14)
45 Shadow Priests (top is #14)125 Druids (top is #1)
62 Monks (top is #4)
53 Paladins (top is #18)
Rogue representation is 4.3% at 2200+, but only 3.9% at 2600+, so it's not like the class just has a comparatively high skill cap.
Rogues also have the 2nd lowest rep on the ladder in 2s and 3s (Warlocks are lowest in 2s, DKs lowest in 3s).