I think the easiest way to balance the melees would be to make skills more dependent on all stats...not just the three prime melee stats (str, dex, con)
First rebalance the melee so it is balanced for all race/classes...After rebalancing, it is fairly easy to give reasonable justifications for nearly any change...for example the hitroll one:
Str-based: You have the power to move your weapon around easily, able to change swinging angles quickly, etc
Dex-based: Fine motor skills allow your to slightly adjust your striking angle to bypass the enemy's defense. Superior speed/reactions give you the extra time to make the strike...
Int-based: You superior tactical knowledge gives you insight on how to penetrate your opponent's defenses/armor. You know where and how to hit them. Feints and any other tactical skill...
Wis-based: Using your battle experience, you can easily predict what your opponent will do next. All defensive reactions and their counters are ingrained in your skull. The experience to know when and how to USE any tactical knowledge you've learned...
Con-based: By controlling the energy output of the fight, you can move both slowly AND powerfully along with bursts of speed/strikes. Superior constitution maintains the steadiness of your weapon/arm/footwork and gives you consistency in your attacks, even as your opponent becomes tired...
Power, speed/reactions, knowledge, experience, consistency
Any one of these could be a reasonable justification to use that stat (or a combination of them) for hitroll...
