I've recently had a few map gens where Billy nuke after Billy Nuke has destroyed t3 armies, bases and wills to live.
https://replay.faforever.com/23361723 Here's one game as an example.
To me I see 5 issues with the Billy
1 - its really cheap, for the cost of a couple percies you can have a tactical nuke.
2 - it has 4 HP thus if you want to push a t3 army in and your not Cybran you'll have to build 4 TMD again and again.
3 - it does 12k damage so one-shots all T3 units.
4 - The minimum launch time is 30 seconds.
5 - Tele Billy is insane.
Some possible solutions to the problem?
1 - Instead of 3k mass cost for the Billy missile, I'd recommend increasing it to a minimum of 6k and preferably 8k. This is because a well placed Billy in a core base can easily destroy 15k+ mass and Billy shot into a t3 army can reliably get 8k+ mass destroyed, if the armies big enough.
2 - Reduce the Billy Nukes HP down to 1 so that people don't have to spam up as much TMD when advancing with t3 armies. (Also increase Aeon TMD range, because at the moment all tactical missiles fly so high that they go right over Aeon TMDs vertical height, if shot outside of t2 pd range from the TMD).
3 - I'm okay with the damage but would recommend giving T2 mobile shields the ability to not get over-matched by a Billy Nuke. As a note overlapping shields stop a Billy, but singular mobile shields will not.
4 - Increase the minimum launch time to 1 minute and increase to build time to load a Billy for an unassisted T3 ACU to 1 minute so you can launch a Billy at a t3 army to deplete its shields then do it again 30 seconds later before the shields have a chance to recharge.
5 - I'm shocked that I haven't seen tele Billy get used more, yes its expensive in energy, however forcing your opponents to shield everything and TMD proof everything is worth the cost, not to mention teleing inside of shields. As a note if the Billy Nuke hits the inside of the shield it doesn't detonate and simply disappears. I suggest moving the teleport upgrade back to the back.