It uses the same engine that Dead Island and the Call of Juarez games use, just the latest version of it I assume.
Yep, it's the Techland engine.
There are several other videos already published. When I find the time, I gonna look them up and post.
They used some HEMA dudes for the motion capturing and to advise them on the combat. Doesn't necessarily mean that they get the combat right but it indicates that they seem to focus quite some time on it.
If the combat is good, I wouldn't mind a shallow skill tree tbh.