Well, I can't endorse your policy of using orcs to populate your territories

, but I agree that generally the orcish units perform decently.
Raiders and snaga archers, though... I never use 'em, except as Dunland, and then only as a "distraction" - I send a stack of the trash orcs into Rohan to draw away Rohan's stacks from my invading army.
Champions are good, indeed. I also like the Uruks - the Swords are fast, iirc, and there are a lot of 'em; and the Spears are decent in some situations.
But the Uruk Halberds are *excellent* in the right situation. For me, that situation is a defensive bridge battle against Rohan. They are great at hacking down Rohan's cavalry, especially when said cav can't pull off a charge in the cramped space of a ford or bridge.