Not sure if it's related, but I've been having serious problems with act two as well (see my post on cut scene hangs). I use an I7 windows 10 and an HDD rather than an SSD. No problems at all with the HDD so long as I keep the graphics on medium. A lot of people with older computers also have an HDD for storage. If you do then you might want to try using it and turning down the graphics (which still look great IMHO).
