Novalith Cannon's are a bit overkill. As of now the only defense from them is on the TEC side. Both the pirates and advent has no defense.

so I'd like to propose a suggestion.

1) Pirates should be given a Planetary Shield Generator with full upgrade's.

2) Advent need a way of shielding their planets that uses the Hardened Cities upgrade, either increase the already existing defense % or grants secondary upgrade based off the hardened cities research called Shielded Cities that increases the defense further.

TEC can easily afford to defend against both the Novalith Cannon and the Deliverance Engine, the Advent have no defense vs the Novalith.

For example, during a game vs. 2 AI opponents, 8 Novalith Cannon's were obliterating by "one shot's" my entire empire in short order.  Advent need a better way of damage adjusting, their planets.

My suggestion would be to increase the effect of hardened cities to 20% / 40% / 60% or create a secondary upgrade called shielded cities, that increases the already existing 5/10/15% by and additional +15 / +30 / +45%  it's not as good as a planetary shield 20% 50% 80% and might be expensive in comparison, but will survive a single Novalith projectile. In response, the TEC High Yield Warheads already penetrate the defenses of Hardened Cities by 10/20/30% so no adjustment would be necessary to counter common bombardment defenses.