Why would we want to dumb down this game more?

If you understand your job, you dps and time cool downs to provide dps, watch eminity meters, and use your job to its fullest potential.

If you just want to play casually in tank stance 24/7, that's fine to, all the 4 man dungeons were designed for you.

If tanks just had tank stance mitigation 24/7, you wouldn't need cds. Or eminity combos for that matter. The way the game is now at least.

If anything you DON'T want this because they would gear new content around your new mitigation, and you would HAVE to learn how to manage your cds, or just die even with your constant 20% mitigation.