BM definitely has real problems right now, but you are mischaracterizing the problem by focusing on DPS, and by using Mekkatorque as example.
First, Marksmen is the 3rd best DPS spec on Mekkatorque out of 24, Survival is 7/24, BM is 12/24: still better than half the specs in the game on that fight.
Second, it’s not accurate to say casters are dominating that fight, and especcially not to say DoT casters. Shadow, Balance, and Fire are all adjacent to BM as being average DPS on Mekkatorque. Affliction is the outlier at 5th, but it’s actually Demonology Locks (pet class) that dominate Mekkatorque: not Affliction (dot class).
Third, I’d argue it was the 5% aura nerf in 8.1 that wounded BM hunters that you are feeling, and not the azerite ring discrepancy. Every class I follow has issues with the azerite traits and rings: it’s not a unique problem to BM, and it doesn’t explain the magnitude of decline from last tier to this tier - but the aura nerf perfectly describes the problem.
Lastly, I would reconsider what you consider a weakness for certain classes. Mekkatorque is not so movement intensive that it hurts casters. And good casters are the least impacted by movement - because they stutterstep during instant casts. And top parses have a strong inherent bias to the casters who were not forced to move much during a fight: so the caster who didn’t need to move all fight will get a top parse for their class, but this bias doesn’t apply to BM.
By focusing on top WarcraftLogs, you are filtering BM hunters by (best)gear and performance, but you are filtering movement-impacted casters by essentially gear, performance, and luck. The benefit of BM being virtually immune to movement DPS losses, is that BM has far greater consistency of performance than caster specs, for what that’s worth.