Observations so far on the new Defense research tree enhancements for defensive structures:
- The TEC Gauss cannon upgrades are definitely worth the money and get the job done. If I saw a grav well stopped up with fully-upgraded cannons, I would want to bring the new anti-structure bombardment frigates to deal with them. You can wipe out upgraded defenses with a straightforward attack, but your lost frigates are more expensive than their lost cannons.
- I'm not so sure about the flak upgrade for hangars. The range of the flak is pretty small, and a hangar defense is itself already an "antidote" to strike craft if you build fighters.
- The Vasari upgrade for missile platforms is terrible. It's basically a very, very bad damage over time upgrade, except incapable of killing anything. Also, the debuff flickers on and off when a target is under attack; it appears a ship will regain its regeneration when a missile platform starts shooting at it, then lose it again when the missile SFX actually hit.
- Again, I question whether I really need the Vasari upgrade to let hangar defenses deal with strike craft. In my experience, if an opponent has brought a significant carrier force to attack my planet, my hangar defenses are so wildly outnumbered by hostile squadrons that resistance is futile and the only hope of defense is to bring warships to attack the enemy carriers. On the other hand, if the only hostile strike craft are 2-3 squads from enemy cap ships, then a hangar defense's fighters can neutralize them already and any upgrades would be wasted.
- The Advent upgrades are fairly useful - the bonus shields help out structures (and, more importantly, add a level of shield mitigation). The bonus shield regeneration from the hangar defense upgrade is helpful to starbases. I don't think either upgrade makes a large difference - 150% of a beam platform's damage still isn't a big number, and the shields go down fast compared to the heavily-armored hull points of structures - but a cluster of Advent defenses is fairly tough to kill.