Strength:
Main role: "clean" amount of melee damage, sum ups with weapon stats + modifiers/skills
Secondary role: maximum carrying weight, heavy weapons (STR requirement), critical [tied with dexterity]
Affects:
Chance to hit (melee/ranged) [less then dexterity]
Damage (melee/ranged/magic)
Armor penetration

Dexterity:
Main role: armor class, ranged damage
Secondary role: evasion, critical [tied with strength], chances to hit [greater % bonus then strength per point]
Affects:
Action points
Chance to hit (melee/ranged)
Chance to be hit(melee/ranged)
Damage (melee/ranged/magic)
Critical hit chance/damage
Evade

Intelligence:
Main role: magic damage, INT requirement
Secondary role: dialog modifier?
Affects:
Willpower
Damage (melee/ranged/magic)
Charisma (dialogs)


Speed:
Main role: speed movement (in battle [too])
Secondary role: attack speed?
Affects:
Initiative
Cost of movement (can be argued if DEX instead)
Evade (less than DEX)

Constitution:
Main role: amount of HP/mana
Secondary role: ?
Affects:
Damage absorption (melee/ranged/magic)
Willpower
Mana/Energy
Plenty of resistances


Perception:
Main role: uhm accuracy?
Secondary role: something on the field? Enemy discovery? View of field?
Affects:
Charisma (see a lot os small details about chaarcter and env that helps in dialogues)
Initiative
Chance to hit (melee/ranged)
Evade (possibly)



This is just a quick one, I'll revise it later, but as you can see I like to tie them up for better balancing for each class. Each main ATTR affects wide range of second attr, some greater (prolific, like DEX is obviously for Evade), some less (STR gives critical hit boost to, but DEX gives more, obviously, it helps to lay down all this strength), etc.


Quote
I liked this part: Critical hit chance/damage - Melee = Dexterity, Ranged = Perception, Magic = Intelligence


My thought exactly, for each specified class - main ATTR increases critical. But... problem is that if you add some artificial non-battle requirement that will force player to increase ATTR not important for his class, like, STR for ranger in order to carry more gold/items, then it does not sounds so great anymore. I dunno this is the problematic spot when you need to be careful.