They would need to redesign tanking all together. Mitigation is "hit this button before this attack". Mitigation isn't hard or interesting in any way in this game. Push button, take less damage. It's exceedingly rudimentary. There's no way to "test" tanks in any meaningful way because there is no meaningful active way to mitigate damage. The only tank stat is hp. So you litterally gain no actual mitigation by playing turtle. More hp doesn't reduce the amount of heals you need.

Ironically it's the reason I like war. They have a mitigation resource to actively manage (wrath). It makes it far more engaging than push button, mitigate damge style of pld. (I haven't messed with dark much but the mp management sounds interesting for the same reason). That's why I still say war is the best designed tank. Managing resources is what makes jobs interesting otherwise they fall prey to a rotation. And there is almost no practical difference between a rotation and a priority system. They both end up brain dead ways to play. Actively managing a resource with tradeoffs gives you DECISIONS to make. If I do X now I can't do Y later. Tradeoffs are what make interesting gameplay. Rotations and priority systems are just reactions. There's no thinking involved with either. Prior is skill 1 then 2 then 3. I just did 1, 2 is still up therefore the next thing is 3. That's not 'thinking' that's reacting. There's no decision without tradeoff. "If I use infuriate to get 1 mire fell cleave under zerk now, will I need to for ib the tank buster in 40 sec? Can I afford to pop vengence just for a stack now and give it up for the next 2 min? When an choice to do an action costs you in some other way down the road you have to think ahead and weigh the pros and cons. Rotations and prios are just synonyms for pattern gameplay.