After all those heartfelt conversations between Myka and H.G., all the understanding built up this season, it comes down to one thing that comes out of the blue--H.G. is completely crazy. Not just the normal "I'm going to resurrect my daughter" crazy, but the "I've been planning to destroy humans to save the world for over 100 years" crazy. Her reasoning fails completely, making less sense than a gesticulating monkey, and Myka making quick work of her felt equally trite, though I'm curious as to where she'll be incarcerated.
After H.G.'s demise, which could have been drawn out longer and thought out better, there's a long cooling off period where Claudia breaks down, Kelly leaves town, and Myka voluntarily leaves the Warehouse, knowing she can't operate after allowing a villain like H.G. to take advantage of her.
I haven't read anything about Joanne Kelly departing the show, so I think it's safe to say Myka will be back. Like Artie's "death" at the end of the season, this is just anything hitch to get the audience riled for nothing.
From what I can remember of the first two seasons, I'd say that both seasons are about equal in terms of quality. The second season really hit some high points, but also hit lower points, and was overall more dynamic, whereas the first season was never great, but never bad either.
Score: 8.0/10