I think both sides screwed up with The Dominion first contact debacle. As stated earlier, Starfleet should have investigated the territory around that colony before they allowed anyone to settle there.
And Dax, a science officer, replying, 'you're crazy if you think if think this going to stop us from exploring the Gama Quadrant'.
I think she was right anyway, but don't say it right then and there. (Technically, the planet wasn't in Dominion territory)
All it did was provoke them.
Still, the Dominion just went and annihilated the entire colony without so much as a warning. Then they go to the station and inform them of what happened.
No wonder the Founders keep getting targeted every few years.