I actually just released a pretty large performance boost, which is likely why you're seeing those higher speeds again after so many patches.
Congrats on completing Act I! I'm really glad the transition into Act II landed for you. I wanted it to feel genuinely disorienting going from being so established and powerful to suddenly having to figure out what the rules even are again. That feeling of "wait, I can just die to this guy?" was very intentional.
Don't worry too much about the amount of new stuff all at once. Soul Forging and the other Act II systems are meant to give you room to experiment with them as you go rather than needing to understand everything immediately.
And you've got quite a bit ahead of you from where you are now. Thanks for sticking with the game this long, and especially for all the feedback you've given me along the way!