Is it a traditional tragic ending if some of the guilty parties escape? Because if there was one character I really wanted to get it, it was the 'blind gayboy', and he got off with no further injuries!
I was enjoying the subversion of the traditional resolutions - like when Fiennes shoots Gleeson in the leg because 'I had to do *something*'. From then shooting him in the neck onwards, it just seemed to revert to type a little, though there were still great moments (especially back at the B&B).
And above all, I didn't feel harrowed at the end, or any sense of catharsis. I'm remembering the laughs, not the deaths. So if it was intended tragically, I think they misjudged the tone.