The AI in a LAN game in Dawn of War: Dark Crusades, rushes you within five to minutes as will, while also taking into consideration stategic points, critical points, and technology upgrades.
If they were to address the issue with the AI in Sins, then I would have to say, they'll need to fix, everything.
1) the AI don't attack unless they outnumber you.
1a) they only attack with maximum numbers, and ships such as heavy cruisers and caps, when both are destroyed, then they fully retreat.
2) they don't take into consideration, that holding a star, and not the planets could easily boost their defense of their worlds while they upgrade all areas within technology.
3) mostly they take worlds, defend with minimal numbers, then move their fleet around to bogus positions on the game, which are easy to pick up on, then counter follow their movements.
4) Stardock is too specific on what types of AI are to be in game, overall they should have it to where the Ai are both aggressive, technological, defensive, and economic.
5) It'd be more challenging if they AI didn't focus on allying with you, and focused more on getting planets fast, moving their fleet after taking a world or defending it until it's at max upgrades, and building support is finished.
5a) to make it more interesting, I'd like to see the AI focus on upgrades, then once they've built up to their max in technology focus all res, on you and only you.
6) it'd be interesting in game to see all AI ally with each other, and focus all ships, and such on your only world(s).
Stuff like that I guess, there's more to it, but as always it's a insufferable task to just think on them all.