I'm afraid you and I part ways here.

For my money, characters good enough to be worth writing about almost demand at least some control over their destinies. Denying them that only makes whatever the planned plotline is feel forced, to the writer if not the readers.

Also, I honestly didn't have a problem with the resolution to the Trinity love triangle. I admit one of my reactions on reading For Today was "It took you long enough!" but beyond that no. Honestly, saying that Anthy's motivation was simply 'let's get this crap over with' oversimplifies, if not cheapens it as well. It had to be downright painful to see the two most important people in her world hurting themselves and each other over her feelings. She said as much. Given some of the other working though unconventional couples around and Anthy's growing attachment to Corwin in her own right, the solution was pretty obvious.

So in short, in my opinion it did indeed work, because it fit the characters and was the logical culmination of that particular plot arc.