I think it should only fire once every 2 minutes(or perhaps 2 minutes and 30 seconds.). It is currently a siege cannon, and while this is alright because you can see where the projectiles are coming from and it counters 'indestructible bases'(which can take a lot of firepower to destroy), it is also very cheap and powerful. It will likely in total do more damage than 3 nukes, which it is worth less than.(Not including the added cost the nuke launcher itself would require)

At the moment, if you get 2 omegas, you can take down almost(if not) every building every 30 seconds.