GNB is the tank that get's the better DPS at the cost of mitigation. Now with that said I find it can be the most mitigation heavy tank in the game next to PLD. I find myself constantly cycling rampart, camouflage, nebula, aurora, heart of stone. You can quite literally have a mitigation going at all times, and you should since GNB's rotation isn't stupid tight like PLD is.

GNB damage is high and mitigation is supplemented by it's oGCD's being another rotation in and of itself.

Other tanks can get away with this as like PLD. The rotation is so strict to fit in your goring blade, Circle of Scorn, Spirits within, Attonements that you only have time to throw your mitigations in weaves. PLD's opener is literally it's rotation and you have to keep it going through a whole fight. During PLD burst phase you have to weave in your Sheltrons with Holy Spirits/circles and Sprits, scorns and not miss your Confiteor.

GNB to me has a much looser rotation outside of your burst and allows for filler during it's burst phase i.e. rampart, aurora, HoS, camo, nebula. But you have to keep that mitigation train rolling, which is where the GNB challenge sets. I always start a fight with Rampart (get the mitigation train rolling), Bloodfest (setup for burst and Burst Strike finisher), Rough Divide or Lightning Shot (depends on pull), into No Mercy.

Once you pop your No Mercy you better have 1-2 cartridges, spam your DOT's, Blasting Zone, Continuation burst, finish with Burst Strike. Rampart should last the whole opener then it's back into your 1,2,3 combo with Burst Strikes for effect. Once Rampart falls off it's Aurora, heart of stone (best during 1,2,3 combo for Brutal Shell buff), Camo. I TRY to save Nebula for tank busters if I can, but sometimes you need to use it. GNB just has two rotations...it's attack rotations and it's mitigation rotation.