Here's the thing with the archon and the incubi. The incubi are so good that they really don't need the archon as company. What they need are grenades. Is there a cheaper way to get them grenades? Yes. The best way to get them grenades in my mind is to bring the baron. He is cheap and can maneuver quickly to get them grenades if they need them. The archon is cool, but he doesn't add that much to the squad beyond his grenades. The Baron is a boss and adds a bunch!