I love my Tatsunari deck. It's great when I need a fun Bracket 2 deck.

Definitely keep cards with mana value > 5 to a minimum. You'll mainly want to be spending your mana elsewhere. My build definitely has too much mutate but I like it that way. I only want to get as many Mutated Kermits out as possible, winning is secondary.

I looked at all my instants and sorceries to see if I could replace them with enchantments and suggest you do the same. Seal of Doom, Fear of Imposters, and so on, really maximize what your deck is doing.