As an added benifit, you used no forces or resources to attack that planet, and had no risk of losing your own forces or planets in the process, because you kept well defended.you dont seem to get my point you can kill the planet but all of its defences are still in orbit and you have to plow through them to get to the planet.
No I do get it - I just dont think you are thinking of it as an opportunity, insted of a staple building. A strategist wouldnt bulid a heavy artillery emplacement to destroy a closeby rampaging guerilla force, you'd use it to wipe out a known enemy position. Everything has its own place in the field, and its own time to use it. It has plenty of use, but if you dont see the value in it thats your thing.
You dont have to necessarily hit that ONE planet and wipe it out, there are almost always plenty of other targets of opportunity. Besides, at that point the tech tree taking out a planets defenses shouldnt be a problem for a TEC "never-die" fleet with Comand Cruisers, Repair Cruisers, and Flak Frigates. Also remember it becomes more useful with allies in larger games, and with all super-weapons it isnt as useful in small games, because they usually lack the tech or the economy to justify it.
(and as a note, no race, including Vasari without 7 or 8 of their super weapon on a single target, can clear out an enemy planet of all its buildings and fleet at once. Sure it can clear out that fleet and planet buildings, but more than likely the enemy is just as fortified at that point of the game at other planets, or they are aiming super weapons at you too)
The point of a strategy game is to look at what you are working with, and figure out a way to defeat an enemy. There are lots of ways to use the Novalith, listed in an earlier post, but if you are looking for a different kind of super-weapon maybe you'll want a different race?
Each racial super weapon has their own way of destroying the enemy economically and/or militarily. TEC destroy the planets population and remove the resources, manufacturing ability, tech research ownerships, and destroy credit income through population loss (which is a very big deal on high-pop worlds). It is very crippiling to the enemy if you have 3 or more of them, and usually if they dont have a super-weapon its game over.
Advent love-me-cannon is a giant problem to enemy economy, and with the right research for culture you can gather intel on other planets, and abandon planets. That gives you the economic advantage and intel advantage, so you can plan where & when is the best time to strike an economically inferior enemy.
Vasari's weapon does damage to enemy fleets and buildings anywhere in the galaxy (solar system is much quicker) at anytime, to prepare for an upcoming assault (which they will most likely win now), or to feign an assault at another location. It also wipes out undocked strikecraft, which combined with their warping abilities, different tech tree bonuses, and total phase jump detection makes them the ultimate terrorist-tactics fleet ; since they have the information, damage, crowd-control & "anywhere-at-anytime" military force.