I'm going to gripe about Spire Stealth Battleships (in addition to Maws and Gravity Drains). Mostly because Stealth Battleships, having radar dampening equal (or less than) their attack range makes turrets useless against them, and fighters take forever to kill them.
Gravity drains... Gravity guardians are one thing, but they're rare. The AI gets gravity drains, and you can kiss your entire fleet goodbye because you can't run away or even get into attack range with short-range ships.
Maws - if anything, I wish they digested my ships faster if anything. Seriously, it's kind of annoying when they eat 50+ of my fighters and then run away and I have to wait a while to be able to rebuild, and I can't go hunt the maws down because then I won't have any fighters left to build for a while because they'll all get eaten too.
Rams I haven't had a problem with - I've found them really easy to kill, and they're kinda slow. Blade spawners I haven't played against, as with the other spire ships (armor rotters, tractor platforms, gravity rippers...)
Before I respond, I would like to mention I think of fleet ships being dividing into four tiers:
"Starship like": Starship like caps (and low limits for the AI on number per planet and per guard post), costs, attack, and survivability. A fleet ship in name only, so to speak. These include (but are not limited to) Spire Stealth Battleships, Spire maws, and Spire blade spawners.
"Almost starship like": Noticeably more expensive and noticeably lower ship caps than the triangle ships (also with limits for the AI on number per planet and per guard post, but at a higher order of magnitude), with increased attack and/or survivability to make up for it. However, not tough enough to "play" in the starship tier. These include (but are not limited to) Zenith Electric Bombers, Spire Gravity Drains, Spire Armor Rotters, and
maybe sniper ships
"Normal": Similar in cost, attack, ship cap, and overall power as the triangle ships. These include, well, most of the fleet ships, but the bomber, frigate, and fighter serve as the reference stats for this tier.
"Swarmer": Low cost, low health, low attack, high ship cap. The "zergling like" ships of the game. These include (but are not limited to), Laser gattlings, Infiltrators, most melee ships, and Neinzul younglings (though for some reason these have normal ship caps).
Anyways,
Make sure to think of Spire Stealth Battleships, Maws, and Spire Blade Spawners more as starships than as fleet ships. Their stats and ship caps are balanced according to those level of units. They will seem much closer to balanced when you think of them that way.
Also keep in mind that the huge number of them that the AI is currently using is a bug. The next version will enforce the caps they were supposed to have.
I do agree with you that thanks to how major gravity effects are, Spire Gravity Drains should rebalanced to be put into the starship tier, with correspondingly low caps for the humans and the AI.
EDIT: Oh, and I agree that the HP of the Spire Stealth Battleship could use a bit of nerfing, as their stealth and radar dampening already provide it plenty of protection.