The last part of my general Core fix
is fixing the rogue.
Rogues are interesting, in that they are both a bit underpowered (in combat) and overpowered (in that it is too easy to use skills, particularly Diplomacy, to the point of brokenness). Therefore, this is both a nerf and a boost:
The boost (based on suggestions by NeoSeraphi):
Note that the nerf is not meant to make skill use useless, or even unbreakable. It is, however, meant to make them roughly as possible to break as they are in real life.