Bring a Kodo Beast
Kodo Beasts have an aura that enhances the surrounding Orc units' damage. Build them and bring them along. They can also Devour enemy units. Make sure you also research War Drums to further enhance the War Drums Aura.

Get Tauren with Pulverize
Tauren are very powerful with Pulverize. They are the most powerful ground melee unit. If you are facing advanced melee units such as Knights or Druids of the Claw, you need to move up to Tauren to combat them.

Use Raiders
Raiders are needed when facing air units and for attacking enemy towns. You can also gain resources with their Pillage ability. Raiders quickly destroy buildings so build at least 4 of them and use them to sneak in, destroy a building, and run. You'll find Raiders are often better than Demolishers for killing buildings.

Use Spirit Walkers
Spirit Walkers have various purposes, they best work in combination with Tauren. In fact if you plan to use Tauren, they're a must have. They can also be used for their Spirit Link ability which helps your units to survive longer when they are under focused fire, and they are great for scouting while in ethereal mode, which could also help you to buy items from shops that are still guarded by creeps if you've researched the backpack upgrade.

[ Click to Enlarge - 180 KB ] Here is a nice army for 1 vs. 1. Certainly this isn't the only combination...	[ Click to Enlarge - 145 KB ] Two Orc Players create a mix of Troll Berserkers, Demolishers, and Grunts.