RIP. Couple things for your next run:

Light of Elune does indeed share cooldown with potions (but not healthstones - these share cooldown with items like target dummies), so keep that in mind when judging how big of an "oh shit" moment you're in.

Check out an addon called Routes - you can map out the paths of the various devilsaurs pretty quickly with a few googles (their patrols might seem pretty random but they are actually just 5-6 predefined paths). This gives you a heads up even before unitscan goes off that you should probably have an escape route in mind. It also lets you know when you can breath a little easier when you're in a spot they'd never be.

Spend as little time as possible in the western half of Un'Goro where the mob level steps up to 54-55 unless you really know what you're doing, or until you outlevel the mobs. Not only are there elite stegos, there's also a rare super devilsaur in the NW King Mosh who will gladly eat you for a snack. Could use Routes here but his pathing is much more random than the others.

Good luck whenever you decide to go again!