I haven't touched the story and I don't know when I'll be back to play the game. Maybe there will be a patch where healers get some adjustments before 8.0, or it might only be when 8.0 launches, or maybe even that will fail to address healers in any way that matters to me. My point is just, I haven't seen that fight, but on the topic of mobility in general...
Funnily enough, the suggestion that I've been making for how White Mage could feel better for DT would actually help with that. What I was suggesting was for PoM's cooldown to drop to 60 seconds, doubling how often you get Glare IV uses, give Dia a 15% chance to proc a use of Glare IV outside PoM windows per tic, and for you to be able to hold 3 procs at a time. This change would give you more access to an instant cast nuke that could be used for attacking and moving at the same time. It's "more complex," yet gives you more personal utility. And to compensate for all that extra damage, the potency of Glare III and Misery would go down, which has the added benefit of reducing the pressure on White Mage to maintain DPS uptime as using things like your Medicas, Regen, Cure III, or even Raise becomes less punishing on your damage output.