My concern is the min versus max. If everyone starts with a 5 attack, bare-fisted, but has a 20 with a warstaff, for example, that's only a 4 to 1 ratio, i.e. not too bad. It certainly looks better than 15 versus 0.
As for defense, Say you have a Staff (5), with a 5 bonus from str. That's 10 factors. Facing another 'staffer' in Leather (3+2+2+2), that's a 9 def.
Pretty even odds there. if the attack has a 6 attack (sword), that's an 11, but with the wood shield (-1), that's still only a 1 point advantage (but keep in mind the extra attack from the +1 speed bonus). The spearman has a 14 attack (really should only be 13), facing a 10 defense (shield). That'll cause damage pretty consistently.
Versus the 17 defense (light plate), a WarStaff would have 20, so still an advantage.
I definitely agree Armors need to be tweaked, though. I'd say no armor: 1/4 Con as defense (so a 10 gives you a 2.5 def). This incidentally allows unarmed units (pioneers) a little defense, and a 5 versus 2.5 when duking it out unarmed. The 1/4 Con should be applied to armored values as well.
Cloth (2 breast, 3 arms/legs/cap = 5 Def. Add 1/4 Con, you get 7.5, or equal to a Club (5 + 3).
Leather (3 breast, 1.5 each arms/legs/cap) = 7.5 def. Add 2.5 Con, you get a 10 on the defense, or equal to a staff (5 + 5)
Chain (4 breast, 2 each arms/legs/cap) = 10 def. Add 2.5 Con, you get a 12.5 defense, or slightly better than an axe? (6 + 5). Note the drop in dodge skill though...
Light Plate (4 breast/lesser dodge penalty, 2 each a/l/c with dodge penalty). Same as above, but you are slightly more nimble.
Heavy Plate (5 breast, 2.5 each a/l/c with dodge penalty) = 12.5 + 2.5 con = 15. Slightly higher than a spearman, equal to a sword (10).
Light Master Plate (6 breast, 3 each a/l/c with dodge penalty) = 15 + 2.5 con = 17.5. A 12-13 str weapon would be comparable.
Heavy Master Plate (7 breast, 3.5 each a/l/c with dodge penalty) = 17.5 + 2.5 con = 20. A War Staff (15 + 5) would be comparable.
Legendary Plate (8 Breast, 4 each a/l/c with dodge penalty) = 20 + 2.5 Con = 22.5. An 18 point weapon would be comparable.
Heavier armors should have correspondingly heavier dodge penalties, and perhaps speed/move reductions as well... when is the last time you saw a fully armored knight able to chase down an unarmored spearman?
At one time, greaves, armlets, etc. DID have fractional values, hence my using them in the formulas above. Or maybe I'm thinking of another game, but as you see, they work!
Also note that Con becomes a little more useful... and that Str/2 is applied to all weapons, not (Str-10)/2.
Also note you could have 'Bruce Lee' as a viable option now: 20 Con/4 = 5 def, 20 Str/2 = 10 attack. OK, maybe in this case Con/2 (10 Def) would be better, but then you'd have to add another 2.5 to the attack values of the weapons to compensate... I'm actually OK with that!
Boosting all weapon strengths by one or two points would favor the attacker a little better. I wouldn't go much past that though, using the above values.
This would help mitigate the square/squareroot a bit, which I feel pretty passionately needs to be done.
I did NOT include shields, because I think they should be handled by a separate block roll. I also think their Def values should be higher, so they are actually able to reduce significant amounts of damage (not just one or two points),
Also, we need a dual weild rule, and a change weapons action as well for heroes, but those are subjects which have already been brought up elsewhere...