These unnoticed and eternally-active acts of theft & violence eventually bogged down the game. The more a player commits those acts, the more the game is trying to keep that all up to date and in memory, and so the more slowdowns start happening. Essentially, the ‘DM’ eventually becomes unable to operate. By Act 3 this caused slow-down issues, which after some sleuthing we’re extremely happy to say we’ve solved in Patch 5, which is in testing and scheduled to release this week.”
I sure hope that's the real issue here.
I'm running a (non-Durge) Paladin on my current play-through and other than the occasional five-finger discount, I haven't really done any "criminal" stuff, so I doubt I have a huge amount of unpunished crimes hovering above my Tav's head.

I've also avoided any actions that could've broken my oath - I only just now found one instance that will break it and that was telling the weird fish-priests near the Foundry "I'm not getting involved" when they're trying to get me to kill the submarine captain. Time to hit F8, of course...

Anyhow: I still feel this is at least in part related to certain areas on the map: The Lower City Wall waypoint for example will *always* make the game hang after I teleport there - while other waypoints in Act III do NOT trigger slow-downs.
S.