I bought the Danny storyline, largely on the back of one thing: that post her being attacked by Jill and then by not being believed by anyone for a while, Val was susceptible to anyone who came her any kind of positive treatment, even if it turned out to be horribly false charm. Should Karen and Mack not briefly have trusted him? Absolutely, but his problem was that he was putting his best face forward, and sociopaths can be diabolically clever. But should she have trusted Gary instead? Yes.
I noted in the past that Gary and Val remarried in episode 300, which I don't think is coincidental. That's why I think the whole brain-injury plot line was cooked up; to delay it until late in the season so it could happen in the milestone episode number. Of course, 250 episodes is also a milestone, and they could have been remarried then. Episode 250 occurs right in the middle of the Sally's Friend plotline.....
Still, I think Season 11 worked very well, even if it was Knots at its darkest. I'd definitely take it over the concurrent season 9 of Falcon Crest.