i just went to act II to test it and upon reaching the required lifespan for 5000x speed i can run at around 4500x to 5000x on dedicated worker here
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).