But you insist that the bracers allow Kivan to do more damage to the enemy and I say if he gets them the effect is Immy does less. I say that Kivan does enough damage already and Immy doesn't. They are not competing to see who does best they are shooting at different enemies and trying to stay alive so to take the bracers away from Immy to give them to Kivan when he doesn't need them is a waste. He already gets more attacks per round so he is already going to take down his enemies faster and does not NEED any help to do so. On the other hand while he is taking down his enemy if Imoens enemy is taking fewer hits then it stays alive longer and has the potential to damage other members of the party for a longer period of time.
You are only looking at how wonderful Kivan is going to be and not looking at the downside to Immy NOT being more useful when its possible to make her so and your theory that with lower enemies that can be taken down in a single hit it doesn't matter who gets them shows that. I say in that situation it DOES matter becuase if Immy can't hit them she can't take them down and Kivan can only target one at a time
no matter how good he is. So Imoens MISSES can have as large if not larger detrimental effect on the party as Kivans prowess can have a good effect.
Now put that in your little calculator and crunch it...
I also think its mumbo jumbo to even speculate that it would be possible to mathmatically account for every possibilty in every battle...