Well define "problem." Once you get to the "cap," it would be impossible for anyone to pull threat from you anymore without a taunt, right? They would have to pass you by 10% or 30%, depending on range. So what this really means is that once you get to a certain point in the fight, no one can pull aggro anymore. How is this different from what we have already? If you already managed to hold threat through 20 million threat or whatever, you aren't likely to lose it anyway, and then it just comes down to how much DPS you can do as a tank and cycling your cooldowns appropriately, which is what you'd be doing anyway.
Kathy, I said, "I'm lost" though I knew she was sleeping
I'm empty and aching and I don't know why
Counting the cars on the New Jersey Turnpike
They've all gone to look for America