I really like all these feats! Some of them will really make a world of difference for certain builds. I do have some comments:
Fighters:
Greater Weapon Focus
Type of Feat: Combat
Prerequisite: Must be a fighter, base attack bonus +13, Weapon Focus in the chosen weapon group.
Specifics: The character gains a +2 bonus to all attack rolls with the chosen weapon in addition to the +1 bonus given by Weapon Focus.
Use: Automatic.
In NWN2 and the 3.5 SRD, this feat only adds another +1 and has a pre-requisite of
Fighter level 8. I don't object to the feat being stronger, but would you consider adding this pre-req? This is quite a potent feat that I don't think should be available to any Fighter dip; Fighter 8 sounds like a fair commitment to earn this Feat.
This pre-req would at least give a pure Fighter access to this Feat earlier than most Weapon Master builds. It would be nice for pure Fighters to have some early strengths compared to WM builds.
(References:
http://www.dandwiki.com/wiki/SRD:Greater_Weapon_Focus ;
http://nwn2.wikia.com/wiki/Greater_Weapon_Focus )
Overwhelming Critical
Type of Feat: Combat
Prerequisite: Must be a fighter, Str 18+, base attack bonus +17, Cleave, Great Cleave, Improved Critical (in chosen weapon) and Power Attack.
Specifics: When using the weapon chosen, the character deals +2d6 points of damage on a successful critical hit. If the weapon's critical multiplier is x3, it's +3d6, and if the multiplier is x4, +4d6.
Use: Automatic.
This feat is also more powerful than the NWN2 / 3.5 SRD versions (which do 1d6 damage less across the board). This seems a little more questionable since it really looks like a crazily good choice for Weapon Masters, a class that I don't really think needs more help in the damage-dealing department or in popularity. Yes, it costs a lot of Feats -- which will probably keep it out of reach of Rogue/Fighter/WM builds. But it will be a no-brainer for Fighter/Weapon Masters.
If the purpose is not to boost Weapon Masters too much, could we instead gate the Feat through a base class Pre-req, e.g.
Barbarian 8 OR Fighter 8 OR Paladin 8 OR Ranger 8?
At least, that's my first impressions looking at those two feats.