They have toyed with this already. Stopped using vit as a damage stat so that they could independently adjust health and damage output as needed over time. For example, if they need to tune tank damage up (or down) they can just adjust the strength on gear without it impacting our health up or down without having to confuse the playerbase by changing behind the scenes stats in an obtuse way.

2.0-3.X: Str was AP. Fending Accs were junk. Pentameld/Str accs were king.
3.X-3.9: Str/Vit were AP at .45 each. Tanks were happy. DPS tanks were happy, Turtle tanks were happy. Devs unhappy trying to balance content.
4.0-Now: Str is AP again, removed tanks off str gear. Pentameld king again. People unhappy again (but not as much as 2.x)

I don't particularly like the way they have done this (looking at you dumpy accessories), but there is some merit in that line of thinking. But there are no shortage of alternatives that avoid the pitfalls of the current situation. Mostly because Tank accessories are crap again and watching tank gear drop in raids is depressing when they are worthless.

The simple solution is keep str the same, but redistribute it between left and right side so it scales with ilvl more evenly and all slots are valuable. instead of 100 str on all 5 left sides and 0 str on right side, make it 50/50 (or whateer the exact numbers needed to match the design used on DPS/Heal AP but slightly lowered for tank needs) so all ilvl upgrades are valuable. You can keep AP and Health independent for balancing. You can stop making pentameld low ilvl crafted gear BIS. Raid drops will mean something. Turtle tanks get to wear vit gear. DPS tanks get to wear vit gear. No more gap between gear playstyles splitting the community and making PUG/Roulettes annoying.