I don't think adding a Summoner's Pact would help, you have the Fauna Shaman some Ponder or Brainstorm would help you to get the combo.

Why this deck have 4Hedron Crab ? In the description you only talk about it with the Paradise Mantle . Drop both of them, add Birds of Paradise , you'll have the mana and you can add 4 other cards.

In my opinion 4x Sands of Delirium and 4Blue Sun's Zenith are to much, 2 sands and 2 zenith will make you have almost 80% chance to get one before 4th turn and with the Brainstorm 's or Ponder 's will be easy to win.

This deck have a great idea but don't do well against fast decks or control decks, counter top deck will be a pain in the ass, show and tell will be hard too.

Now I saw, this deck is modern not legacy, forget about the show and tell and counter top deck....

Hmm, what if I added in Fog to help counter fast decks?