Disco should have high trajectory, and more EMP and Slow damage so it get a higher DPS that can draining and eventually pass shields like Starlight.
AND my favorite option for it that will never be implemented, the "unit cannon".
Zenith should have meteorites of various size, in addition to the actual small and fast ones, there should be a bigger one that have more that 3600 damage to bypass shields and fall every 30sec (or more, 45sec ?), some more intermediaries, and maybe one similar to a nuke every 5min (or more, 7min? 10min?).
Starlight = Precise Atk and a good Def vs Large units like Det etc.
Zenith = Sure base killer after a time.
Disco = intermediaries between the 2 and maybe a Def vs big army of small and cheap units (yeah, i never see big army of cheap units working in late game too...)