I could see your strength bonus limited by the quality of the blow. I mean, if you just nicked it for a single point of damage, should you be getting +4 damage to that scratch? Yes, you *could* say that the +4 damage represents your ability to push your weapon closer to the enemy, and thus the scratch on the elbow instead was hitting center of his arm and cutting it off completely. But you could also say that the cut on the arm is just a cut on the arm, and your great strength was misdirected due to a poor attack.

Proposed rule, if you wanted to consider it:
Strength bonus to damage cannot exceed the actual roll for damage.

That way, the nick on the arm is a *teensy* bit worse, but it's still just a nick on the arm.

Alternate proposed rule, if you want to get messy:
Strength bonus to damage cannot exceed the die roll over the number needed to hit.

Therefore, if you exactly what you needed to hit, and no more, then you get no bonus to damage. If you roll 6 over what is needed to hit, you have room for up to +6 strength bonus. This rule could also be adapted for other types of bonuses, for obvious reasons.

Either of those two options could get you what you are looking for, IMO.

*~*~*

Or, if you want a third alternative:
Leave the system the f**k alone. Too many little rules make players unhappy. Unhappy players rebel, or at the very least lose interest and stay too focused on the rules, and not on the roleplay.

Of course... I've not been very good at following that advice... :)