Lots of unclear stuff in the rules in new version:
1- What's the health and damage of the doppelganger, does it mimic the highest you flipped? Or the lowest?
Yes, this isn't addressed in the rules. From the designer's Kickstarter comments though: "The Doppelganger minics the life and attack power of the enemy it is next to. If it is the middle card, it mimics the stronger card, but no bosses."
2- When you defeat a boss card, does it go in your discard pile or with the treasure cards? I don't see a reason why it would go to the discard since there is no item on the reverse side.
This is in the rules on page 10, at the top.
3- What does "banking" a card mean, it doesn't say anywhere in the rules when you should do it, and what it is.
This is in the rules under "Gameplay" on page 6, step 3.
I have the game, but I grabbed the rules here: https://greygnome.files.wordpress.com/2014/03/odd-rules.pdf