Haste and mastery have always scaled synergistically, though. Stacking mastery was the biggest misconception of T14. This goes to GoSac scaling as well.
I get what you mean though and I completely agree. They need to make mastery affect pets somehow like increasing damage on their special abilities. GC replied to someone asking for this and he just made it sound like they have bigger concerns to take care of. I guess someone needs to tell him that letting our pets as Affli/Destro benefit from mastery would solve the gearscaling benefits of GoSac that will keep make it dominant talent choice at the end of tiers (or even earlier).