DedWards

Seeing that the format has a 49 card deck (the commander doesn‘t start in the deck) and the normal starting hand is 7 (ignoring mulligans), that leaves 42 cards on the start or 41 on the draw. With do few cards, I'd be tempted to play mill with a few extraction spells to get rid of the shuffle back cards. The other option I'd go for is a pure aggro rush strategy to get as much damage from a cheap commander (like Rhys the Redeemed or Ezuri, Renegade Leader) as soon as possible.

Assault Formation could be nice to help get Doran's effect without Doran being there.

As for vs tribal, a lot of them make tokens, so I think Bile Blight and Echoing Decay might be good options.

I've never played Tiny Leader, so take my suggestions with a pinch of salt.

Sadly, I'm struggling to get Battle Hymn, so I have yet to test it. Although, we don't really keep to a format in our group games, so the build I use then has a full play set of Seething Song and Right of Flame in addition to the other rituals. I've had turn 2 wins off storming into 4 Kokushos and a Predator Dragon :P But, the group kicks the guy who just won through mass killing of all opponents (he still 'won', technically) so as to make the game continue and be fun for everyone.

I was kind of pushing for mono red, even if I'm using non red / hybrid Gitaxian Probe / Manamorphose, so adding another colour may call for a complete redesign. I will admit that the deck originally had a set of Bogardan Hellkite and 2 Hunted Dragon as its win condition, but experimenting had me shift to Kokusho.

Have you thought about using more dragons yourself? I've often though of adding a single Knollspine Dragon to replenish my hand after storming into some Hellkites.

Dashing through the pain
Onward as we slay,
Chopping as we go,
Laughing all the way.
Foes' ears will ring,
While they run in fright.
Kolaghan's lighting sings
A slaying song tonight.

That's why I added Predator Dragon, search for it last and devour the last of the Kokusho's for the final 5 life loss. I remember storming 6+ spells in 1 turn, so adding 2 extra dragons made sense.

Funny you mentioned Empty the Warrens + Battle Hymn, I recently posted a mono red Dragonstorm deck using that and calculated how to cast both Empty the Warrens and Dragonstorm in the same turn.

http://www.mtgvault.com/dedwards/decks/dragonstorm-modern/

Goryo's Vengeance is an awesome card that I don't own :(

I'm sad that Seething Song was banned in Modern :'( They're practically forcing us to play UR to storm (for Goblin Electromancer)

On another note, I've been adding Gitaxian Probe and Manamorphose into all my Dragonstorm designs for 'free' draws.
My Dragonstorm runs a set of Kokusho, the Evening Star instead of Bogardan Hellkite.
Because of the change to the legend rule, specifically the part about keeping one, I also added 2 Predator Dragon.

Empty the Pits would be cool too.

I've seen people use Heliod's Pilgrim to search for Presence of Gond. And you can search for it with Congregation at Dawn.

In my Midnight Guard + Presence of Gond deck, I decided to add some extra redundancy:

Sigil of the Nyan Gods + Devoted Druid can make for an extra Midnight Guard. Plus, when you combo off, the Sigil allows for you to potencially attack for lethal in the same turn.

In case, for whatever reason, Presence of Gond isn't available, I also included Sprout Swarm. Because it puts a creature onto the battlefield, Midnight Guard untapps; because it's a green spell, Nettle Sentinel untapps (I also use Nettle in my deck), and because the creature count went up, the Sigil allows for an additional untap of the Devoted Druid it is on. Just 4 of these untapping effects can allow for infinite casts of Sprout Swarm, just tap the 'new' Saproling for the next casting's convoke.

Because you're relying on winning off Maze's End and all the Guild Gates enter the battlefield tapped, I strongly suggest upping the number of Amulet of Vigor and Rites of Flourishing to at least 3x each.

I personally prefer Etherial Haze over Holy day as it can prevent damage from outside of combat, Like Vexing Devil's 4 damage option.

Dictate of Kruphix might be a good card to look into. It's Flash option allows for you to choose who gets to draw off its effect first.

Another 'Fog' that I've come to like, even if only as a sideboard card, is Batwing Brume. The black part is awesome against Splinter Twin decks :p

I also suggest rearranging your lands so that you increase the lands that can produce the colour mana that you actualy use, the rest are only really needded for the win factor of Maze's End.

Mesmeric Orb would be cool in here, especially with an Undead Alchemist out :p

Seeds of Strength - it targets 3 times, causing 3 heroic triggers.

I don't quite see how to create a storm count with this. Besides Dark Ritual, you don't have any cards that net you mana.

Blood Funnel makes your NONcreature spells cost {2} less, so Myr Retriever will still cost {2} and Priest of Gix will still cost {2}{B}, thus not getting any free mana from the Priest. Now Heartless Summoning, that makes creatures cost {2} less and can make an loop with Myr Retriever and turns the Priest into a Dark Ritual.

And I just checked the rules for Spellweaver Helix, due to the wording of the Oracle errata, you can't loop two Helixes (assuming they have the same sorceries imprinted on both) as the errata says that a CARD must be cast for it to trigger.

I've never been fond of this Lili putting the land into your hand and not onto the battlefield. But that could be because I was running a Korlashs, Heir to Blackblade deck when she was printed and I needed the swamps on the battlefield asap. Besides Korlash's Grandeur ability, I also use Wayfarer's Bauble to get the swamps onto the battlefield.

With all the mana in here, especially from the Shrines, why not include an X mana spell like Exsanguinate? Would make for a nice, over the top finisher.

Some interesting choices. I have to ask though, why Stab Wound and that particular Lili?

Also, have you considered some cheaper kill spells like Dismember and Go for the Throat?

With the number of tokens you should be producing, Mass Polymorph might be better than Polymorph.

I've been wanting to run a similar deck and while looking up cards for the idea I came across these:
Myr Landshaper - can turn only lands into artifacts, but help as additional copies of Liquimetal Coating.
Magnetic Mine - 4 damage to the controller of the destroyed 'artifact'
Splinter - exiles and extracts all cards with the same name as the 'artifact'.

Sorry, just ignore this. I had a blonde moment ._.

Sadly, I suck at sideboard construction, so I can't help you there.

Honestly, I'm not sure. If you do add them, I'd say high dash to effect cost should be on top of the list to be removed, this means keeping stuff with key effects. I'm even not sure the equipment is necessary, it feels like more of a cheap trick than something really useful. I'd go with 3 to 4 Impact Tremors and 2 to 3 Outpost Siege. Vaultbreaker seems a little expensive and Mardu Scout's 1 toughness makes me not like it as much.

On another note, with Urborg being legendary, 2 seems a little iffy. Odds are low, but drawing the second one is a dead card.

Lastly, I really don't like this version of Zurgo. His abilities definitely don't belong on a legendary creature. They're stuff I'd expect on a common.

Impact Tremors and Outpost Siege (calling Dragons). Damage for your creatures entering the battlefield and for them leaving the battlefield :P