I feel that i have quite bad possibilities to do good dps as a Sin. Played alot of Bg:s so far:

Warriors: i dont do enough damage to be able to take them down.
Mages: On occasion i manage to pin one down long enough
Clerics: A joke, they practically ignore me and continue healing. Their dam shield and HoT, Insta heals are easily taking out my puny dps.

Im not saying things will not change as you go up in level and it might be very different. But so far its crap to be rogue at this level. Especially if you are lvl 36 in lvl 31-39 bracket BG.

I tried speccing as a marksman but i would like to try out a melee rogue since i have a lvl 50 mage pvp lvl 3 already.