My reaction was pretty much the opposite. The first film didn't make much sense, and the final twist was hard to predict because of it. I didn't care about the characters at all.
The second film was more logical. For some people that meant it was also predictable, but for me it was about right.
The third film was again a very logical development of the first two. It felt more like the last part of a trilogy than a second sequel. The victims were not very likeable but then they aren't in the other films, either. That's kinda the point and is part of why they are chosen. The core of the film is the relationship between the master and the student.
The gore was much like in the previous films. Nothing made me wince as much as the hypodermic needles in the second film. The plot twists, also, were not any cleverer. If anything it seemed to be they were compelled by the story they wanted to tell which arose from the situation at the end of the second film.