And how is the vasari siege capital ship vs other capital ships? They look badass but I have never used one

Vasari are masters of phase space. With their phase missiles, No ones capital ships are safe. They are by far the most dangerous faction to expensive ships and structures. The devastator isn't the best siege cap per se, but is certainly nothing to scoff at. IMO it is better than the marza at lower levels, but is overtaken by the Marzas power past lvl 4. I know many people who like to do Devastator rushes, where they get two devastators as fast as possible, sneak them behind enemy lines and destroy the enemy home world before he can get to and destroy them. With the current build, I dont think any of the races truly suck, but Vasari are incredibly dangerous late game, and are dangerous to capital ships early game.

I don't understand, you would think if the ship was at a higher level it would do more damage.

Disintegrate. It damages shields, hull and AM of target unit and restores the shields , hull and AM of the devastator. It was semi recently buffed and is now pretty decent, though its utility in general was never very good. Kind of a glorified egg nanite bomb. Don't get me wrong 1v1 its one of the best cap ships and would certainly stomp its TEC and Advent counterparts of equal level, but when do you ever have caps fighting 1v1?

its the colloquial term for the evacuator's lvl6 ability

Ya know I never figured out what the vasari cannon does, Does it emp everything in the blast radius? I was hopeing it be like the novalith

Do they suck?  That mostly depends on whether or not the player playing them sucks at playing Vasari.

I think they are a little weaker than the other two races early-on in the game and don't do as well if they get into fistfights early on.  They are stronger in Entrenchment in these regards since they have the most useful starbase.  Later in the game after they have researched more military technologies they can become very dangerous and very powerful to the point where they can challenge Advent battle balls.

Every now and then two lone opposing caps will end up in the same gravity well.  It can happen sometimes.  If the opposing enemy capital ship is a high level Vasari Evacuator (the Egg), then you should probably run away unless you have a Radiance (which will remove the Egg's ability to fire nanites).

Vasari are probably the weakest faction at the start of the game, and the strongest faction towards the end.  Between phase missiles, phase stabilizers, subverters, and the Kostura, Vasari are absolutely crazy in the end-game.

You can't compare the Kostura to the Novalith.  The Kostura is simply in another class from the other superweapons altogether.  Its first effect is to create a phase stabilizer at the target planet.  If you have phase stabilizers researched, this enables you to jump directly to that planet.  In other words, you can directly invade any enemy planet you desire once you have a Kostura.  Its second ability is to damage and stun every enemy unit and structure in the target gravity well.  This does not affect friendlies, and you can fire the Kostura in to the fight.  If you have 5 or 6 Kosturas, you can vapourize the entire enemy fleet like this.

Dude, the vasari cannon is the best superweapon in the game!

I think all of them look cool, but looks don't really have anything to do with it.