Just a note, brd's foe requiem is still worth it even in groups without casters, since that boosts the healers' dps (a reason why speedrun groups take drg/nin/mch/brd).
In terms of utilities being nullified, well in easier contents it doesn't really matter since in the first place you can get two of the same jobs in the party. In the harder contents you can make RF require one MT type and one OT type in the queue, just like how RF enforces at least one of each type of dps (melee, caster and physical ranged). For statics/premades we already see most groups having one war and one pld/drk, nothing really changes. I agree that it's less than ideal (compared to every tank being equally good at MT/OT position), but it's a lot easier to balance I'd imagine.
If we look at the state of healers right now, any combination works (whm/sch, whm/ast, sch/ast) since ast can switch between two stances (shield type and regen type), but imagine if they add another new healer. Is the new healer (and every subsequent healer) going to have two stances too, leaving whm and sch as the odd ones? Or are they going to give whm and sch two stances too? I honestly have no idea how they'll go forward from this point.
Eh not really, as MT war is kinda inferior compared to pld/drk, for magic busters we only have thrill (which isn't a big mitigation on its own) and vengeance. With high defiance uptime yes war has a really good mitigation, but there's a reason why people don't have wars tanking in defiance for a long time. The only fights where warrior is good in the MT slot is where the tank busters are spread in a way that you can holmgang every alternate tank buster (like a12s), so you can stack thrill + vengeance for the other ones. There aren't many fights where bringing double war is optimal.
