I think their insistance on categorizing support roles into two main archetypes (i.e. PLD vs. WAR, WHM vs. SCH) has hamstrung design creativity since ARR.

I get that it's done as a balance convenience, but unless role subtypes are enforced this will likely backfire again. Both tanks will need to be active at some point in any given fight, or else you start looking at solo tank comps. If an OT tank job can actively tank equally well, then you start thinking about bringing two OT tank jobs for better raidwide mitigation unless those counters are adding a lot of extra dps.

The starting point for design shouldn't be to get players to play in a specific way. You need to give them tools to experiment with and see what they do with it. I'm more impressed with what they did with the DRG jump having mitigation attached, because that's the sort of risk that I would rather see them take.