Everything below is possibly wrong... even very wrong. But then again this is the forums after all.

Noticed that recently I seem to be getting moved to a previous position quite often.
As if the client and server are in disagreement as to where I am and then renegotiating so to speak.

If you take the above possibly true (even though its anectodal) it may explain a few things:
Say they made a game with an awesome combat system.
Say further that in order for the combat to work they needed to trust the client to do more of the work.
This opened the door for bots. Perhaps not unexpected but perhaps the sheer scale and the intensity of the exploits turned out to be a surprise.

The price for fixing this problem is reduced combat efficiency. Larger overheads all round since you have to check the client for veracity.
So with one thing and another you end up with a steadily deteriorating fps.
Now getting the performance back without recreating the other problem may require a lot of work.

Just a thought. Probably wrong.