I am seeing the same behavior as well.
I have avg 30ms latency on Lothar, and notice considerable lag performing certain actions.
- Mount/dismount - Sometimes I will either be swimming in the air, or trying to fight a mob, but it says I am still mounted; even though there is no appearance of being mounted.
- Quests with special action buttons lag to register. For example, picking-up a water bucket to put out fires. Even the world quests to reclaim azerite.
- During combat spell actions fail to register, etc.