AST main. It's been a lot of oGCDs since at least Shadowbringers.
Valorath
Basically agree with Pyros that you lean into your oGCDs as much as possible. Don't underestimate Ewer; it's a 1000 potency heal over 15 seconds on oGCD. If you don't want to use it on a tank, it's also great for the one idiot DPS that stands in stupid and needs to be topped off (but not immediately).
Weave Intersection as much as you can; it's a small pot heal, but it acts as a stall that lets you keep DPSing with your on-cooldowns. Opposition should be used pretty much on c/d for trash pulls even though it's a "group/AoE" move. Also, don't forget about Exaltation.
You can Horoscope at the end of a pull, then use standard Helios or Conjunction to proc Horoscope Helios for your next pull. If you have an impatient tank who keeps running ahead of you when you cast, Swift is now on a 40s cooldown.