On the Raid Starship usefulness fluctuating, that's interesting, I'm guessing it's related to the guard post buffs. I don't think I've touched the Raid's stats themselves since before the last official version (other than to add mkIV/mkV).
I probably do not use raid starships in the intended way, lol. They are almost always doing lots of things all by themselves while the fleet is elsewhere. Here's the sequence as far as I remember it....
1) They were initially very amazing for killing entire planets no matter what mark it was. They'd fly in and avoid the masses due to speediness, blow up the guard posts, blow up the command station, and the entire population of the planet would then drain out into the waiting hoard of defenses and turrets.
2) Back in ye very olden days when planets would spawn more turrets as the progress increased, they became somewhat less useful as AI progress increased.
3) When guard posts initially got their HP upgraded into the hundreds of thousands, they became pretty much useless.
4) When they got their attack bumped up so that the six mk-1 and mk-2 of them can kill a level 1 guard post in 2 volleys they became super awesome again.
5) Gravity guardians and gravity drain units make them sad, so their usefulness depends a lot on whether the computer has lots of those.
6) The armor changes seem to have made them pretty fragile, since their hull is 'ultra-light'. They die incredibly quickly to MLRS, missile, and anti-starship guardposts, so I have to be kind of careful these days. Mk1-Mk3 raid starships cannot take out a shield guard post by themselves but add mk4 in the mix and it goes down pretty fast.
7) They can no longer take out an entire Mk-4 planet by themselves. This is probably intended.
8- One of my favorite strategies is to make a SC jumpship, stick my raid starships in it, and warp it to a data center or coprocessor deep in AI territory and blow it up for a nice progress reduction. This is usually a noble sacrifice because the jumpship tends to attrition, blows up, and leaves them stranded. They usually get deleted fast because their presence angers the computer. I can't do that this game though, cause no asteroids.
EDIT: 9) Forgot to mention, they take a lot longer to build now so glorious suicide runs take a lot longer to recover from.
On a separate note, my homeworld in the uber AIP game was initially boxed in by two mk4s, one of which had a raid eye on it. That was fun to deal with.