Admittedly, buffing heavy armor is the farthest thing from most NA players' minds considering how frequent and annoying it is to deal with on our end. I'm curious though, what causes you to think it'd need a buff if such changes were to be implemented. Not at all trying to be malicious, I am genuinely curious.
Perhaps it's because I am EU, and the heaviest stuff you usually see is Kuyaks. Kuyaks everywhere. I hear their drums in the dark. They already took the two handers and the polearmers. We have hidden in the chainmail area, but we won't last long. They're coming!
On EU, almost nobody uses plate, and considering their cost, the really heavy armours like coat of plates and above are not really worth their upkeep and weight. On the other hand, there is little use in wearing light armour, you receive almost the same damage like naked. If you spread out the armour values quite a good bit, I think things would change a bit. Infantry with their heavy armour would become a little bit tougher, which is nothing bad in my eyes considering the hard time this class usually has (on EU, at least), and on the other hand there would still be a point in wearing light armour instead of a shirt.
Spreading the weight values a bit more according to the armour values would be totally fine, though, to limit the extend of the armour buff a bit.