My point was the station needed a ship. Stationing the Defiant there was the best use of resources they could do. It fit the roll perfectly.This is just made-up. You're the one always going on about how much it costs to build a starship, and here we have one that has a non-standard warp core, the latest shipboard phaser technology, quantum torpedoes, ablative armor (which requires REPLACEMENT/ patching after every mission,)
Why place a Nova when you could just leave the Defiant where it is?
To start with Sisko pulled it out of mothballs where it was doing nothing. Then the area got dangerous and not only that but the crew knew how to use the ship. Removing it would have been a bad idea.