The whole of orc defense can be summarized in a few words:Don't do it if you can help it. Sure, many of the same techniques on the Human Defense Strategy Page can be adapted to orcs. However, the basic orc defense is to survive until you can get bloodlust, then annihilate your opponent. There isn't much to it (which is most of the reason that orcs are so popular). There are basically two ways to stay alive long enough:
1. Build a ton of grunts before going for stronghold.
2. Build a few grunts (5 or 6) and a farmed-in cannon tower,then go straight for fortress.
Use whichever you like, but we have found that #2 works the best, especially if you can get a quick jump on the enemy. After that, it's almost purely all-out offense. Note that, obviously, no matter which one you do, you should keep doing your normal tasks (building farms, upgrading weapons and armor, and the like). Orc defense is one of the easiest concepts in the game.