In Dawn of war Soulstorm i usually play space marines and i try to get a SR and an OR so i can get a librarian, terminators and terminator assault squad, then i buy a Chaplain and grey knights (and a commander if you dont have one)
I attach the librarian to the assault terminators
The chaplain to the grey Knights
and the commander to the terminators,
I put all of the terminators in the Barracks (Deep strike)
Then i send the grey knights to find the enemy base so the terminators can deep strike into the field
And annihilate your foes
I also Play Tau and i usually get 2 hammerhead gunships and up to 6 sky rays
But if you want a defensive i can get 2-4 Battle suits (not crisis) ,3-6 firewarrior teams and a couple of pathfinders (for those sneaky buggers)
But i play Eldar as well and i always cloak my base and maybe build more than one then i get as many warp spider teams as i can for a fast but deadly attack
but these tactics can also be used in Dark crusade and maybe in 2 (never played it)