I'm of the opinion that Raid Starships do too well in that kind of "wolf pack" deep raid. They should do well, but as Spymine's experience shows they do *too* well. I think it has a lot to do with the AI not having sufficient weapons that actually hurt them. Like many people, I think HBC's should hurt them, at least on a direct hit, but I need to ask Chris about that since he's the one who gave them aoe-immunity.
As for multiple-homeworld starts, they should be balanced almost exactly the same as a multiplayer game with that many human players (I say "almost" because the multiple-HW version is a loss if you lose any home command station, rather than all of them). While playing an 8-player game with really well-coordinated players is likely to be easier than a single player game for a variety of reasons, it shouldn't be way easier. Same deal with an 8-HW game.
In practice, however, this can be difficult. For example, someone playing an 8-HW game who builds Riot MkIIs to cap (24, I believe, in total) all with tazers has an aoe-paralyze weapon of doom. In that case the tazer should probably have a (reasonably high) max-targets-hit thing, but anyway. Same deal with an 8-player multiplayer game in which everyone unlocks Riot IIs. All that said, even such exploitable ships have a counter; the Riot IIs aren't terribly durable and can only paralyze a localized area. Raid starships are a lot harder to counter right now, short of grav drills and whatnot (and even then it's a pain to actually kill them).