It made sense to me that Damar could work with Kira at the end.
At that point, he was a strictly utilitarian mindset, and so was Kira. Kira needed Damar to rally Cardassia against the Dominion. Damar needed Kira to teach him now to fight a superior force. As much as each hated working with the other, they were both rational enough to know they had to do so.