I believe you get 12 mages regardless, the runes just make them more effective, same for the rest of the armies. 50 elves, humans, and dwarves, and 12 mages. Either way, I don't think I did much supplying for any of them, and pretty much used them to keep those minions off of me when they came out. I did get the achievement to keep over half of my armies alive while defending the door though.