I think there's an issue with GNB's kit being clearly weaker than others in regards to taking on tank busters, without a short cd invuln to make up for it and that together with 2 of it's unique cooldowns being shareable, makes it rather unwanted in the MT position. Right now you need to rely more on Nebula and Rampart for TBs while WAR and DRK can spend theirs more on autos and while PLD technically suffers from the same issue, they already have passive block providing constant fluff mitigation.

I think most importantly, Heart of Stone should get bumped up to 20% while used on yourself.

Camouflage is a decent cd for autos, but I'd like the parry chance changed to 100%. This would make it reliable for physical tank busters, making it a counterpart to Dark Mind, while still giving a little bit of fluff mitigation in fights with zero physical damage, unlike old Raw Intuition which became pure Shake it Off fodder in o5s or while tanking Omega F.

Aurora honestly is fantastic the way it is and having it be a regen rather than straight up mitigation feels refreshing. It also synergizes well with Superbolide due to it's true invulnerability effect.

Superbolide is perfectly fine and I've used it to great effect on trash packs, you simply need to warn your healer that you want to use it so they don't heal you until you're at that 1HP. Then they can calmly get your health up with sustained heals thanks to the 8 second invulnerability. Using any of the invulns unplanned and at high HP is already wasteful(yes, even Hallowed), so I don't see any issue with it.

Brutal Shell's shield is really just extra healing potency disguised as something else. The actual effect is literally equivalent to Soul Eater(150+150=300). It's not bad, it's just not anything special - it's on par with the other self sustain combos and that's perfectly fine, just don't think the shield is something it's not.