Consistently Low Backstabs

[Cecily]

Since none of them brought it up directly. It's specificially your str which is low for your level. At 151 you wont be able to 255 cap while buffed. Str effects your max damage and contributes to your atk. Atk determines the frequency of higher damage hits. So you need str+atk to fix your problem.

My recommendations are...
•Epic if you lack it. 20 STR 40 ATK on it. If you don't have one write an apology letter to everyone you grouped with post-52 and get the damn thing. Problem solved. OTHERWISE...
•Acquire enough gear for 183 Str minimum. Allows you to cap 255 w/ maniacal str.
•Ask for / tip for / get buffed. Rogues are one of the worst unbuffed classes.
Key buffs are whatever str you can get.. VoG and CoP.
•And finally get a Goblin Skull Earring. It's useful and a tiny bit of theoretical damage.
•Aura of Battle is the big thing you want later on.

That should help. Good luck!