If they buff Heavy Armor, you have people with God-like defenses. Technically, those people could still use high-speed katanas and would still be at an advantage with you because they take less damage. The only overall concern of poise is that defensive factor, which is only natural of Heavy Armor.
The problem with Poise was they made it to easy, which isn't a natural problem that comes with it, it can be adjusted. They can make poise harder to get and they can make it more costly. Again, the problem in Dark Souls was that it was too easy to get to optimal values. With a nerf to rolling and a hopeful nerf to Poise, Heavy Armor would not pose a problem, especially since it seems they are solving backstabbing issues.