Blueicus, you forget the comment by Weyoun in "Favor the Bold" where he says to Dukat that they need to make an example so they will kill everyone on Earth.
I think the Breen attacked in small numbers because of the easy detectability of large fleets. Remember, warp drive in a solar system is highly disruptive of planetary orbits and would therefore be noticeable, nullifying the advantage of cloaks. Massed ships emitting antimatter plasma would also be hard to hide. As for hitting a planet or sun with "warp" weapons-that pesky planetary gravity thing probably makes it impossible to aim with any degree of accuracy, and who wants to shoot a gun that may or may not hit? If I point a gun at you I would like the bullet to, at least, go in your general direction. If there is a strong and unpredictable chance of it going sideways or even back at me then I'm just going to pick up a rock and hit you over the head-its safer for me and just as painful for you. And Shameless McBundy is right-the attack was a Doolittle Raid. As I said in an earlier posting-I had to write up an overview for a fan fic last week and I thought it out fairly well. Combined with the "official" info from Memory Alpha, that was the only way I could reconcile all of the tech and known details.