I think Katrina had good motivation (eventually) for going evil. Your suggestion about planting more seeds of temptation is a good one. I only wish Katrina's buildup had been condensed. (Maybe by getting rid of the Hawley backstory episode, for one?) Then Katrina could've been a powerful foe for longer, rather than being offed so soon after acting against Ichy and Abbie.

I really liked Grace, too. She seemed so serene and welcoming--a very interesting counterpoint to all the other people of the past we've met on the show.