I haven't run any numbers. I see this:
More Downforce yields more Grip.
More Grip yields higher Cornering Speed.
Higher Cornering Speed means there is less speed to loose before entry.
Less speed to loose generates less braking heat.
Two Car Thought Experiment: (Simplistic Assumptions: - no weight transfer, same weights, brakes, cooling -delta T at the rotors, etc..)
Both cars will approach the same corner at the same speed - Pick a number.
They will both brake as required to make the turn. (May not be the same position!)
Car #1 (with more DF) will take the turn at higher speed due to more Grip available.
Car #2 will brake harder to reach a lower cornering speed to make the turn, generating more heat in the calipers and rotors.
Car #1 retains more kinetic energy, and converts less to heat, faster exit speed. Car #2 finishes as the first looser, all other things being equal. (YEAH RIGHT as if they ever are...)
I might be able to run something on CarTest2K, but gotta work steering arms today first.
Cheers - Jim