Hello!
The sim api for arms warriors seems to be wrong and it might mess up with BiB for arms
This is what the amr sim for arms looks like 
But both simc and my actual logs show a big difference in terms of spell dmg
I know the gear is slightly different there but even with the same gear, the spell priority is a bit weird
I would need a lot more information to comment on this in any way.
You can find the rotation being used by the simulator here in the rotation section:
https://www.askmrrobot.com/wow/guide/class/warrior/arms#generic
The “raw” view from the simulator itself can be found here:
https://www.askmrrobot.com/wow/theory/rotation/amrwarriorarmsmain?spec=WarriorArms&version=live