Why not just make everyone a DPS?

[Reynhart]

But here's the real rub, if you start making tank mitigation super important (even though it is still being checked), WARs will simply take the place of PLDs on the sidelines.

You make both mechanics at the same time.

Let's imagine a big boss who create parts of him. Each time one part is killed, he loses a 10% of its life, and you need one tank for the main body and one for the part.
You could have any tank on the main body focused on surviving high damaging moves (So, any tank with high VIT, but "mostly" PLD or DRK, since damage is less relevant), and one tank on the spare part focused on dishing out damage (So, any tank with high STR but mostly WAR since surviving is less relevant)

You could even alter the main target to switch periodically to either physical or magical busters, thus each tank will have its strong and weak points in the long run, and the spare part to switch between physical and magical resistance so that you want to mix your DPS.
For an additionnal mechanic, you could make the body to keep only one type of busters (physical or magical) when it hits 50% HP, thus managing your timing so that the final from better suits the main tank you have.

[RapBreon]

You make both mechanics at the same time.

Let's imagine a big boss who create parts of him. Each time one part is killed, he loses a 10% of its life, and you need one tank for the main body and one for the part.
You could have any tank on the main body focused on surviving high damaging moves (So, any tank with high VIT, but "mostly" PLD or DRK, since damage is less relevant), and one tank on the spare part focused on dishing out damage (So, any tank with high STR but mostly WAR since surviving is less relevant)

You could even alter the main target to switch periodically to either physical or magical busters, thus each tank will have its strong and weak points in the long run, and the spare part to take reduced damage from physical or magical so that mixing DPSes will be more efficient.
For an additionnal mechanic, you could make the body to stay in one form (physical or magical) when it hits 50% HP, thus managing your timing so that the final from better suits the main tank you have.

You can do this kind of stuff. And MMOs do. But it's a gimmick, you can't fill an entire tier with it. One boss a tier does not make. It's a good idea though, don't get me wrong.

And in the current FF:HW climate it wouldn't work as is. If the current level of DPS checks were transplanted to your hypothetical, you'd still want a tank who does more damage. Build aggro on head, switch to limbs to help DPS.

Your problem is with the tightness of the checks. As I have said, it is binary. Progression through difficult bosses (mathematically speaking) close to release has always been about squeezing DPS to the maximum (single heal Garrosh world first anyone? What a god).

[Reynhart]

Build aggro on head, switch to limbs to help DPS.

Not if you need to keep the part and head away from each other.

That's just an idea I had after 5 minutes, I'm pretty sure a full team of experienced developers can create a lot of bosses with these kind of mechanics

You could also make time kills where the main target has to die around the same time as the last lesser target of a long train. So, killing the main target the fastest is irrelevant.

[Gameplayzero]

I don't get the complaints. The simple answer is that if you are feeling pressured is to just find a group that you can be yourself and go all Vit. It seems that the only time you'd REALLY need to stance dance is during end game, and thats optional. My answer won't change the meta, but for right now its the best thing you have.

Personally I find it way more exciting finding the fine line between "life and death" while also contributing to the team with better damage output. Its more thought provoking and has more thrill. Regular tanking is popping up cooldowns, keeping aggro, and staying alive. DPS tanking is the same, but you are in a more fragile state and are doing more damage. There is hardly any difference. You still have aggro to worry about, and you have to worry more about cooldowns now that you are out of your tanking stance. Its more tanking then actual tanking lol. Your damage also can contribute to your tanking (especially warrior) so thats another plus. This also makes it more exciting/thrilling for healers since they have more healing to do (as long as the tank knows how to properly stance dance and the healer wants the challenge). If your tank is hardly taking any damage then they'll get bored and dps. I don't play healer, but I highly doubt that healer dps will be as fun as tanking dps/rotations :P. Correct me if i'm wrong though.

i'm just happy that they gave us the option to be both.