Whew, this has turned into one of
those topics.
Suffice it to say, I know things are not working precisely the way that I want them to at the moment. A lot of that is heavily playstyle-dependent, though, such that it's hard for me to gauge exactly which rule is taking precedence when, and why the AI is doing X in Y situation. I think mostly this thread has hashed this one out, but as I recall actually we looked at this a lot pre-5.0 and decided not to muck with it too much.
For now, that's basically still my stance -- I don't want to try getting into this one with a ten foot pole until we have a lot of time to sit down with it and really hash it out. During the next expansion development period, I'd really like to introduce some new mechanics to the base game that lead to smaller, more tactical sub-engagements when taking out a specific planet. I'm not sure precisely what will be involved with that. One big problem at the moment is actually the huge range of some ships, most specifically the guardians.
I guess one simple rules change could be to make it so that any ship guarding another ship (that isn't an escort-type ship as with hybrids) gets its attack range cut in half. It might also be that engaging any of the ships guarding the command station is causing the whole planet to bum rush you, and that might need to be changed if that's the case. Those two things might be fairly harmless and straightforward to do, although they'll inevitably mess with difficulty (making the game easier, presumably).
The other issue, about the AI completely reacting to you when you bring in a fleet that is larger than it, is tougher -- that was something that we specifically needed in order to make the game not a cakewalk for really advanced players who were just kiting around killing guard post after guard post while the rest of the planet sat there stupidly, which seemed bad. So that's not really a nice thing, either.
Possibly my goal of having that sub-battlefield feel to the guard posts on planets, like we had in the 1.0-3.0 era, just isn't possible anymore. Back then it always had the drawback of planets being artificially easier because most of the guard posts just sat there instead of attacking you.
Oh, there's also the rule about ships that are attacked being allowed to leave their guard duty when they are attacked. That's been a good fix to a great many issues, but it also causes... well, this.
All that to say, these are the things that I don't have good answers for yet, and why I've been wanting to wait until the next big push of development to really dive into them more deeply. We need time to try things, see what players think, change those things, repeat, etc.