Was the Breen attack on Earth in the Dominion War cynical?
Well if Voyager had an episode where earth was attacked by the Breen then yes, because it would be muscling in on DS9's story and would create problems for them. But as it was, the Breen's attack on earth fell naturally into the story they were telling.
Basically everything you're bringing up is not a comparable example. I mean seriously, why don't you think before you type?
Edit- and not only did they blow Romulus up, the whole story/science behind it was incredibly dubious and unrealistic, just the cherry on top of a fart sundae really.