[Standard] Naya Midrange

So I'm going to assume this is meant to be more of a Naya superfriends deck?  Realistically, you're not sitting on much of a mid-range plan if you only have 5 mid-range creatures (4 Stormbreaths and 1 Polis).  I would suggest digging into more offensive options or switching to more removal.

Another thought, you're sitting on numerous cards that are going to rotate, so clearly you're not making the "rotation safe" folly build (which I'm glad to see), but you're leaving out some REALLY good ones.  Think Domri Rade, Assemble the Legion, even Aurelia the Warleader can be good.  I would also suggest taking a look at Xenagos, God of Revels and Ghor Clan Rampager with Fleecemane Lion to get a bit more of a punch.  Lastly, Advent of the Wurm is another good option.

Where are the Stomping Grounds, Temple Gardens, and Temple of Triumphs?

As for things to cut, I'm aware that Mystics really help, but I'm not 100% sold on them as they're helping with green while you're wanting to hit the other colors more frequently.  I'm thinking the Caryatids might be enough there, but I could easily be wrong.  I would consider taking Lightning Strike out for Anger in the main as it won't kill your coursers while potentially dealing with more threats in a single stroke.  In the event that you don't need the sweeper, you can side in more pointed removal.

For the SB, I would pull Purphoros, Revel of the Fallen God, and possibly even Fated Conflagration - I would actually say to toss in Warleader's Helix as it will likely kill many PWs while also gaining you life against burn decks.

Anywhom, I hope some of this helps.  I know that the combo of Xenagod + Aurelia is pretty sick, accounting for 18 damage in one turn... but if you want to run this other route, there certainly isn't anything wrong with that.  Alternately, you have enough PWs for a more superfriends-style build... at which point you should be running more removal.  Good luck!

My point was that there are a full 2-3 months before rotation, so why not take advantage of standard at its largest, fullest strength?  Obviously don't go dropping $50 on cards you won't use beyond October, but don't just discount an entire block because it will rotate in a few months (otherwise you're handicapping yourself unnecessarily).