I have a tactic to help survive those first few waves of attacks where no matter how right you start out, you always seem to be outnumbered, especially against mega computer opponents. This tactic requires fog of war off though it could be done with it on. When you start the game, depending on which map you're using, send one of your first defensive units out to a point you know the enemy will be coming to get to you. I've never been beaten to that point if it's the first move I make. Now, start doing your opening moves, creating workers, harvest, building, making your army but remember that unit and when you see the opponent moving, use that unit, attack their first unit and then lead that unit somewhere else on the map. If your unit is too fast, you may have to stop and turn to engage them again. By now you may have a line of attackers coming for you, keep leading them further in another direction from your base. It's a suicide mission but I've noticed even after the unit is killed, the enemy continues to advance to the last position your unit was before it died. During all this, make sure your harvesting and creating troops. This tactic has helped me build my army and survive even the Mega Computer Romans and Indians in different two player, mega computer vs me games. I always leave the fog of war off now. I just prefer to see the different factions at work, see if units are stacking up.
As far as the Dark Mages and my defensive strategy in the Dark Magic faction. I make a defensive line of Dark Mages when protecting my base, adding a line of alliyps behind them. This defense proves to be unbreachable. I played this against computer mega Indians and the end stat for me was 842 kills while I only suffered 29 deaths. The Indians just kept coming and my line just kept mowing them down as fast as they could come, rarely even getting in close enough to do anything to my Mages. I would have to come forward to take out the archers until my Mages sight increased and then it just became to easy to defend.
