Why? If your not into epic games then fair enough, but 2v2 on either of those maps is a fantastic battle, provided you have the time for it.
What is epic about 2v2 on Mandala? I've actually had this before in either a Skirmish or Pantheon a long while ago, and your definition of epic is seriously messed up. The map was so empty, I spent almost all the time capping flags, killing random grunts, or contesting the middle flag, occasionally going 1v1 against the enemy Oak. Running back to base to get items took forever too, and the entire game was so slow and boring, took way longer than it should have. I think it was also a conquest game too, so you can't blame it on being a crappy game mode like Fortress or something. And no it wasn't bad because it was pugs facing each other. I've had 3v3 on Mandala too and that was bad, map was way too big for it, so I have no idea how anyone could think 2v2 on the big maps is decent, much less fantastic.
2v2 on Brothers would probably result in either each person going on one side and 1v1 against one of their opponents and of course everything would depend on what Demigod they took. Running back to base on that map takes a long time too.