Polymorph is better with cards like Khalani Gardens, Wind Zendikon, Garruk, etc.
The way this deck is set up, Polymorph is going to be hit or miss. Sometimes you'll hit a T3-T4 bomb and You'll have a total blowout providing it sticks (hard to say with cards like Go for the Throat confirmed). Other times your just going to hit something stupid and waste a card.
I'm not saying polymorph is a bad card by any means. It doesn't surprise me that you would have good finishes with that card.
All I'm saying is that this in particular build is going to be very inconsistent in regards to Polymorph (too many little creatures to hit + extreme lack of removal). But the truth is that we won't know until we see all the other decklists and the unlockables.
I could be totally wrong, but we'll learn more as the rest is revealed. As for Planeswalkers, I would love it if they were added but somehow I doubt that will be the case as the theme of the game is that the player is considered to be the planeswalker (hense the title: Duals of the Planeswalkers)