I agree - warlocks are definitely not OP in arena. The class that is their nemesis, has to be rogues, so I found it rather ironic to be called overpowered by one.

Pre level 66 bg's rogues were pretty much 50/50. If i saw them coming then they were dead. If they got the jump on me then I was in trouble.

Post 66 and that pesky cloak of shadows I considered myself lucky if I managed to get the heck away from them, or if i lasted long enough for help to arrive. I had slightly more success with felguard builds. Mainly for the intercept stun and for the continued melee damage done to the rogue whilst he was under the effects of cloak of shadows and 99% invulnerable to spells.

SL/SL is probably the most survivable spec in arena for a warlock - but gimps the damage massively. It becomes better with a healer on the team as siphon life isn't going to be enough to sustain healing - and lets face it if you are draining life you are standing still and are gonna get kicked. SL/SL was also hurt massively when Blizzard corrected the warriors MS ability (And hunters aimed shot) to affect the healing of drain life.

My very limited experience of arena has been rather negative (a lot of it a gearing issue).. I might stand a chance in a 5v5 team where I can hide in the crowd and rely on others to keep me alive and take out melee but other than that, I'm an easy kill.

I think movement will be your biggest problem as stated earlier. I think a 3 person rogue team would be amazing. I think 1 person trying to control 3 would not have the same effectiveness.