Hahaha, thank you!
It is indeed working now (using cheat engine). I can only imagine there was some issue that occurred when installing the DLC on Steam that must have been resolved after a computer reboot. But I'd never bothered to check whether the log was working for weeks now. After your message I decided to check again, and yeah - everything's now working. This game is incredible, but the mechanics are so opaque that I find the combat log a must-have.