I rarely need more than two. Basically, I don't take them at all unless it's a torpedo hunt mission.

Light is faster than sound. It is for this reason that some people seem bright until you hear them talk.

I always bring 0-2 fuel pods (depending on the mission, and how fast my ship is) and fill the rest of my hardpoints with screamers. I've never needed more than 2 fuel pods, even with the slowest heavy fighters. I would use 0 or 1 with a Mirage, personally.

Oh, and about diverting power to engines--sure, it works great for covering large expanses of space. But when I'm in a dogfight or making strafing runs on a capital ship, and I suddenly need more speed, the last thing I want is to lose energy to shields and guns. So afterburners and the powerball each have their place.