Ok, both 5.044 and 5.045 contain changes intended to fix the performance issues, please let us know if it helps OR if it does not help
In my case, out of the three saves I tried (DrTall's, Kahuna's, and Varone's save), Kahuna's was the only one where I saw what I would consider "unplayable" conditions, and I'm suspecting that's because it's a fairly intense scenario and I was trying to run it on my craptop rather than a real machine.
Tested the latest changes on Varone's save and I was seeing maybe a 15% improvement, but it wouldn't have been that hard to play even without that improvement, even on my laptop-of-questionable-spec.
Thanks for the help!