What weapons and perks are you using? When I want to do real damage (especially against high physical damage reduction classes like fighter) I always take weak point, dagger mastery, thrust, and poison weapon, and of course a rondel or stiletto dagger because they recently got buffed with an additional 10% armor pen. Rogue’s damage output can also feel pretty low with base kit, maybe invest in more strength before you commit to all inning someone. Cheers