I've actually beaten an insane enemy....very hard stuff though. But I used a few tricks like "destroy HQ mission". I was a(guess what?) space marine and fighting with an eldar. And I was playing the original Dawn of War with no add-ons/mods/patches. Sooo bloody....I've killed like two or three Avatars before I deep striked 3 dreads and two squads of terminators in his base and blasted to hell that Webway assembly.
On Winter Asault or Dark Cruasde it's harder...not impossible...but very difficult.

kwl, im gonna have to try it, but go on insane enamy and go against the necrons as the space marines, you really wont do to well on it, its mental the amount of people they send at you, i thought that my defence of grey knights, space marine squads fully armed, four dreadnoughts, a land raider and tw oterminator squads would be enough along with all of the bolter turrets i could buy, and the necrons just came along and battered everything before i knew what was happening, they just slaughtered everything before i could take any action against them

So they drowned you in troops....one word....Whirlwind. It's a divine tank when facing massed infantry(especially orks). By the way...also try using the librarian's "word of the emperor" power when charging into close combat. Your troops will be immune to death for two minutes or something like that. Very useful to turn the battle around. Also bombard the place where you know they usually attack....or place mines in that place. Won't kill them...but will surely weaken them.
Eh enough theorethical advices....when I have the time I will try it and tell you the results.

lol ok, i will try those tactics out as well, if i can build up quickly enough lol im not very quick when it comes to building up, i will admit that i do go quicker on the harder difficulties but im still not quick enough, i think i dont use my res efficiently enough, i ned to plan things out more often as well

Unfortunately very few players are fast enough for an insane enemy(I know I'm not one of them....but someday) but you have to take advantages of a few things like "arrange" your starting position in an isolated area, and "fix" your opponent's location so that you know where to attack when you have the forces. Also never play on an 1 vs 1 map. That's simply insane(). And know whom you're fighting against....eldar/imperial guard/orks means heavy bolter, chaos, necrons, tau means plasma gun. Use the frag grenades as much as possible. I also never leave home without a flamer on each squad and two scout squads with snipers(low morale on enemy infantry is always welcome).

sounds like a good way of doing it, i recently went back on the insane enamy except this time it was necrons vs necrons and we just couldnt kill each other lol it was a stalemate for about an hour before i got bored and gave up, was fun though, watching them trying so much was funny although i did lose quite a few men, but thanks to the necron lord and the ressurection orb, i ended up with lots more men than i would have been normally allowed to make so was able to hold the enamy back quite well

you dont need the opld ones to play it, its an individual game like dark crusade

I have to say that Online is looking increasingly unlikely for me at the moment. My computer's done well for a few years but it's age is finally starting to show. It's really been struggling with my last few LAN matches so I don't have too much faith in it's ability to do online properly. Hopefully summer will bring a chance to upgrade or buy a new one though, along with Soulstorm!