Nearly unplayable lag in savage instances

[RampantRooster]

Starting a couple months ago, I've started getting large amounts of lag inside savage instances. I don't get it in overworld or other instances (including eureka) or even other games. It manifests as the game seemingly deciding halfway through a GCD that I didn't actually press the most recent weaponskill, and it reverts to my previous state in the combo. Obviously, this is infuriating.

Sometimes, but not always, it's fixed by restarting my router, modem, and computer and it generally doesn't come back for the rest of the night. Anyone ever encounter something like this?