the death star was probably too big for the chart, might be a match for vger, sizewise. big ships don't necessarily mean more power. little defiant was a match for any ship but the upscaled dominion cruiser, of which there were not many. it's probably cheaper to build a fleet of defiants instead of a single one of those gargantuan pots. there are scary weapons in the star trek universe, red matter that turns suns and planets into black holes, and what was the stuff soran used to blow up suns called, trilithium? a small rocket. a very small ship can deliver this doomsday stuff.