There's a number of reasons why it won't work either way:
1. Other heals can still be used to achieve the same thing. Even without HoT stack, you can heal a lot with other heals and achieve the same thing. I've long dropped both vigor and regeneration on live in anticipation of it being nerfed, so the changes to HoTs have zero effect when I heal.
2. The problem isn't actually "healing" alone, it's being able to heal the damage done consistently with no real threat of that damage ever overtaking healing -- damage reduction itself in the game is too powerful as well; defense is way overturned in the game. Nerfing healing won't matter as long as there's a way to consistently reduce or negate incoming damage to nothing or under 1000 points.
3. Relative power of an organized group will always be more powerful than a disorganized one because of proc sets and other automated systems like smart healing. This is actually where the most power comes from and it needs to be addressed if they care about balance. But it means a fundamental change in how the game is played, at least from a healing perspective. Not many "healers" will have the skill to adapt to smart healing being gone.
The only probable "true" solution will be to cut smart healing out so that healers actually have to matter and focusing them makes a real difference. When you have the game essentially being half-played for you with targeting and positioning not mattering, then it make it a lot easier to keep people alive as a healer and it lets you output a lot more heals without mistakes than you would otherwise.
When I'm not on a siege (rare), I heal and I can sit on breach and heal with 0 armor rating and have no real threat of dying thanks to smart healing, roll, and the block button. if I'm healing even if it's outnumbered 5:1 and the entire faction with emp, hammer, scroll, enemy ball group, etc. it's not going to matter.
Now, some may say that is skill. That I know healing out the back of my dark mind. And it's true, it's not even stressful in the slightest. But the idea that one person, with no armor and max defile, and even being negated, can still sit on the breach and heal their faction to victory 19/20 times is a problem.
And I can tell you that the secret sauce under that extra cheese pizza is not HoT stacking, or even shielding; it's smart healing that enables so many targets to be covered effortlessly. And until that changes, they will never ever nerf ball groups or the healers you see changing the battlefield.
Fortunately for PC NA and EU I rarely ever do anything besides just fire siege.