Unfortunately, Burton was nowhere to be seen - he had every reason to show up and see why Proctor was under lock-up - but apparently he had no idea that that's where his boss was. If Burton had been on hand, it would have been a much more equal fight, likely without the punishingly tragic ending. (In case you haven't seen this episode, don't read any further.)
The ending unfortunately did make perfect sense in the unfolding narrative of this season. Once Siobhan learned that Hood was an impostor, there were very few viable choices for the series. Certainly Hood leaving Banshee, with or without Siobhan, was not one of them. She could have accepted him and his deception, which is where she was headed when Chayton did his ultimate damage and wrung her neck, but her death was sadly a better way for this problem to be resolved. Now Hood doesn't have to look over his shoulder every time he does something that Siobhan might not have approved of or appreciated.
Still, she was an excellent character, and her murder leaves Hood not only with a huge motive to get Chayton - though he didn't really need one - but a huge hole in his emotional life. What will he do to fill this? Pull close again to Carrie? Well, he was never really that far from her - emotionally - and we've already seen them close. So will there be someone else?
The more I think about it, the more I'm expecting Siobhan's loss to in the long run really change the balance and the chemistry of Banshee. Will be fun to see where this goes.
See also Banshee 3.1: Taking Stock ... Banshee 3.2: Women in Charge ...Banshee 3.3: Burton vs. Nola ... Banshee 3.4: Burton and Rebecca