There are certain concepts within Pathfinder that are rather hard to build and make effective. One such concept is the warrior who fights with a light weapon in one hand, keeping the other empty and eschewing Strength for Dexterity. Mostly this is due to the designers extremely odd aversion to options that allow characters to use their Dexterity modifier instead of their Strength modifier on certain weapon's damage rolls. While I think their reasons for remaining conservative on this issue are rather asinine, I'm not going to focus too much on it because I don't feel like ranting at the moment.
Instead, I thought I'd offer a simple solution in the form of a feat. This feat, called "Improved Weapon Finesse", should help make these kinds of characters more viable mechanically. Also, it'll probably help the rogue, which definitely needs it. Although this is simply a first draft for this feat, feel free to use it within your games and tell me what you think.
Improved Weapon Finesse (Combat)
Due to your training, you are more adept at using agility than strength with certain weapons.
Prerequisites: Dex 15, Weapon Finesse, Weapon Focus (Chosen Weapon)
Benefit: You may replace your Strength modifier for your Dexterity modifier on damage rolls with any finessable weapon with which you have selected with the Weapon Focus feat.