Need help with reducing healer GCDs/mitigation rotation.

I don't have a completely optimised mitigation rotation and I don't know when to use Superbolide/Invuln out side of pinch situations so I would appreciate any advise on general mitigation optimisation or more specifically on Gunbreaker.

Currently on the first w2w I use Reprisal + Nebula (2min cd) then Camouflage after Nebula falls off, along with Corundum and Aurora when health hits half.
On the second w2w I use Reprisal + Bastion then Arm's Length in place of Camouflage.

I am thinking about replacing the Nebula with a Bastion so I can use both Nebula and Bastion on the second w2w but I could be completely wrong about this.

I thank you for any input provided.

Spam Heart of Corundum as often as possible. It's very strong, the heal basically can't be wasted, and it's on a short cooldown.

I don't claim to be optimal or even close to it. But I like to use Corundum + Rampart at the start, use Reprisal after a few seconds, and use Nebula as Rampart falls off. From there I kinda just use whatever is off cooldown, two at a time (Nebula counts as two). And of course, continue to use Corundum as often as possible.

Using Superbolide is tough, cause it's not worth it until you're below half HP, and some healers don't let you get that low. If you know there's one particularly tough pull, just save it for that, and tell your healer before the pull. (Still use Heart of Corundum first, because it's so free.) If you never drop below half HP, then whatever, clearly the invuln wasn't needed.

On PLD I just use Hallowed after my first round of cooldowns, on the second wall-to-wall pull, and again on the last wall-to-wall of the dungeon. (Usually those are the most damaging, and/or people have half their stuff on cooldown for it.)

Oh and I forgot Aurora (as usual). It stacks well with anything, so you can use it at basically any time. GNB has a ton of oGCDs to weave, so I just use Aurora whenever I get a break from all that button mashing.

Personally I make sure my invuln, for PLD and GNB, is the first major cooldown used on w2w trash, before anything else, due to their long cooldown allowing you to get more uses in a dungeon, typically 2 uses per dungeon on w2w trash.

Rest of the time work from strongest cooldown to weakest while using your short mitigation as frequently as possible.

Make sure you don't sleep on Reprisal's AoE 10% dmg reduction and Arm's Length's 20% slow should enemies physically hit you.

Also, you can be nice pairing Heart of Corundum with Superbolide, since you can instantly trigger the 900 potency heal to get you topped a bit.