but if they dont get enof resources, they cant do anything. everything for them costs more.
Vasari do have a great ability to grab neutrals very early and to hold them forever...
and in terms of durability and DPS per cost per supply, they aren't that bad - not quite as effective attrition-wise as TEC or Advent, but it's not crippling either.
also i just want to say this, i find that the Vasari have let me down in one place that counts: their super weapon. i understand it targets the structures above the planet and renders ships near useless, but i think the Novalith has it beat. destroying the planets population and leaving its structures useless is far more efficient than just damaging them. and at least with the deliverance engine you can convert the other planet to your side via rebellion.
I'd consider the Vasari superweapon to be the most powerful of all the factions', actually... for the Novalith, it's easy enough to defend against planet bombardment with a starbase, especially after the time at which Novaliths (or a couple of Novaliths) are viable. And even if you do lose a planet or two, the (direct) cost for colonization of one planet or two or even three is much much less than the cost of a Novalith, especially when you factor in research costs.
But the Kostura is much more effective at assisting at direct assaults, especially from far away. The fleet mobility advantage of the Kostura should not be underestimated, especially in the late-game when fleets are huge.
At least in large competitive cramped games, knowledgeable fleet maneuvering is one of the keys to winning, and the Kostura adds a HUGE advantage to this - especially if you have a level 6 Marauder which can stabilize phase space as well. Even a smaller Vasari fleet with bombers/siege frigates/Desolator(s) can completely decimate an opponent who has a larger fleet, by maneuvering around by using the Kostura.