Now, regarding leveling up a pair of heroes – doesn't it bother you that some Warlock or Barbarian might show up just when the first hero has stopped actively leveling up, and the second hasn't gained enough strength yet? And will be much stronger than them, because all the experience was spent on just one, and not divided between two? And since our army is also split in half according to your method – one has dragons, and the other has everything else – you might end up struggling and not being able to afford it...
Edited: OFF-TOPIC in the message