Given the devastating power of weapons in the 24th century they might have a different view on WMDs. A single photon torpedo potentially has the power to kill millions and no one blinks at their usage. Maybe there might be an element of that in the 24th century humans or the Federation in general have a slightly different view on "WMDs" and what Sisko did isn't considered all that bad.
While we can't be sure--there is a huge difference, with photon torpedoes, between ship-to-ship combat and orbital bombardment. The latter--as we saw with Lakarian City--is
considered an atrocity.
There was definitely in that episode outrage at the idea that Sisko would use a biogenic weapon--the nature of the weapon itself was definitely part of that. So I really doubt the stance towards WMDs has changed much in the 24th century. (If anything, I would have expected that given the evidence that their politics take after today's liberals, that attitude to become even more
stringent, although that's conjecture.)
Back to the post-Dominion War Cardassia, I don't think we've mentioned the fact that the Dominion handed over several territories to the Breen near the end of the war. You would think after the war the Cardassians would want them back. However, I can't see the Breen giving them back.
The Cardassians are DEFINITELY owed there, big time--especially since THEY weren't the ones who handed over said territory; it was Weyoun and the Female Changeling that did it. I have to wonder if the Federation would be willing to strong-arm the Breen to make them give it back?