Androstosity

Probably. Also some duress wouldn't hurt. Maybe 2-4 of those. A first turn duress followed by a second turn hymn will cripple most people.

Hymn to Tourach and Snapcaster Mage.

Elves are almost impossible in standard. Werewolves are cute, but kinda meh. Burn would be pretty fun though.

Ethersworn Cannonist

Deadly allure might be a good idea. It'll kill your own guys to bring them back for another run though the praetors.

Giant growth. Maybe titanic growth?

For anti-graveplay, may I suggest nihil spellbomb? Or how about Leyline of the void? Can't play with the graveyard if they don't have one.

Or anything faster than it. Maybe more buff spells and less hugeness? It'd probably make you even harder to beat as anything could suddenly be huge instead of only what comes out huge being big.

Not using Viridian Emissary? He'd be great for keeping your mana up and for dying for a cause.

I don't think your general goes into the graveyard when it's beaten... So your general is kind of pointless except for colors. Maybe use Progenitus instead?

Is there a reason why you have no doubles of anything?

Just needs Miracle Grow and you'll destroy people.

That's what Orim's Chant is for. They can't attack period. Also, any creatures they have before I get it set up can be zapped away with Swords to Plowshares, on the stick or otherwise.

Why not just run Story Circle instead of all those various circle of protections? Should make your sideboard a little more manageable.

Instead of path to exile, why not run with swords to plowshares?

Can't I use sheoldred's effect to do it? And this is my first shot at a reanimate deck. So if you have suggestions for a replacement for dread return, it'd be appreciated.

Too many omnivores. Can only have 4 as per the rules. Maybe add more mana accel to ramp into bigger hydras from the start?

Love the deck. Niv-Mizzet is such fun to play with. But you might want a way to be able to consistently grab him if you're running him as the selling point of the deck.

Vapor snag over Unsummon?

Make a dragon combo deck. Like thornbite staff + Kilnmouth for a massive machine gun. Or sword of fest and famine + hellkite charger for infinite combat phases.