Might be a PC thing since I can sustain 5000x in both acts after the latest update on a dedicated worker
Viewing post in Cycle of the First Dawn comments
There does seems to be something throttling the game, checked the CPU usage and it barely reaches 10% utilization while running fights; In theory I should still have room to pump up the numbers, but the game just doesn't.
Most curiously, it does actually run at full speed for a few second, before settling back into x3000 (Act 2 fights go up to x4000).