I generally start with a pull with Fight or Flight > Shield Lob > Spirits Within & Circle of Scorn > Fast Blade > Savage Blade > Shelltron > Halone > Shield Swipe > Goring Blade combo > Royal combo > Halone Combo. I also make sure to keep Spirits and Circle on CD or saving it if I need it for some reason. I try to Shelltron at the end of a combo so I can use Shield Swipe as a filler in between combos. If I do get a shield swipe from natural blocking, I try to use it asap however as to not let it go to waste. Not sure if that's optimal or not, but I don't have any issues with my current rotation on enmity, debuff upkeep or DPS.

I found this order upkeeps both Halone and Goring 100% of the fight from the beginning. You can put out 2 combos before having to refresh Halone and the Goring dot. The shield swipe GCDs might mess with this a bit depending on how often you block/use shield swipe.