To the extent that jobs are designed to fulfill distinct roles, some homogeneity is necessary. What doesn't really follow is how much variety they managed to create with other roles, taking either the melee or phys ranged roles in particular - which are all pretty distinct compared to each other - and looking at the complete lack of ingenuity when it comes to tanks.

Regardless, the solution (to me at least) won't be found by splitting OT/MT roles. There are plenty of other directions they could go in without pidgeon-holing specific tank jobs into one or the other "nuanced" differences. It seems pretty similar to the change with shield vs regen healers, where it kind of makes sense on paper but in actual play it doesn't amount to much difference. Certainly not a prohibitive factor. So it's likely this split will be the same thing, not enough to be prohibitive but also not enough to make much difference on it's own. It's an entirely detached argument from the notion of having better/more interesting job design. Like, the foundation isn't even there for that to be the case.