Someone in my fc just came up with a pretty good idea for this, add a riposte/reflect type effect to parry where it returns the amount of damage that you parried to the attacker. Have it cap at 10% of your max hp, so right now PLD/DRK is around 22k with food, the only times you would hit the max damage would be big attacks (melees in a3 are 3kish except for the hand, cleaves hit much harder though). This would make stacking vit/parry a viable option for an MT to be able to contribute to the dps while also helping with the agro lost from losing strength. Allowing us to finally feel more tanky while at the same time our dps doesn't suffer too much.

The only issue is you would essentially kill your off tank dps in tank swap fights, personally I would love to see something like this though so parry is actually useful.