What do you mean by the consistency of Sang Zan's characterisation? He's clearly an impulsive, rather immature man at the start. Then he gets to be Patriarch and seems to be trying to do a good job, but his subjects decide to kill his love in front of his eyes. So ... character change, he becomes a vindictive tyrant. That seems plausible to me. Then he gets empillared, has 100 years of boredom, and comes out a changed man and something of a wet blanket. That is also not implausible.

I guess what I'm trying to say is that the major changes in his character were caused by major events, so I don't quite see them as a problem.

You are totally right about Shen Wei and the hot professor sweat, though.