I think since this a War of the Elements, teams should be required to use a higher % of their element.
I say 70%.
I just think instead of every element playing 50% rainbow decks, they should have to play with what their element has to offer. That is why a person goes through the trials to become a master of a certain element, isn't it? As a master, they should show what they can do with their element, without having to rely on a bunch of other elements.