Muktol

[[Primalcrux]] and maybe [[Khalni Hydra]] could be worth a look.
[[Doubling Chant]] allows you to double your devotion with a single spell.
[[Nykthos, Shrine to Nyx]] is a strong card in devotion decks tough it's expensive to get ($).

Greetings
Muktol

Personally I would remove [[Elephant Guide]] for something more aggressive. [[Invisible Stalker]] is unblockable, [[Silhana Ledgewalker]] only by flying creatures and [[Aether Tunnel]] takes care of the rest, so a creature dying due to combat damage will be rather unlikely. And an opponent who manages to get rid of one of your creatures by spells/ ability's will very likely be able to manage a 3/3 token. Personally I would use [[Rancor]], but that's a budget question, [[Boar Umbra]] or [[Helm of the Gods]].

I would cut [[Anger]] and [[Guttersnipe]] to add [[Goblin Chieftain]] and increase the number of [[Krenko, Mob Boss]] and [[Pashalik Mons]] or [[Purphoros, God of the Forge]]. [[Massive Raid]], or any similar spell, can deal massive damage to any opponent, [[Barrage of Expendables]] could serve as sac-outlet.

Greetings
Muktol

[[Snapping Gnarlid]], ([[Territorial Baloth]]), [[Groundswell]], [[Harrow]], [[Explore]], [[Khalni Heart Expedition]] should be enough answer to that.

Any reason why you're using boros and not simic or gruul as colours?

Greetings
Muktol

Thanks for the explanation :)

Difficult question as I normally concentrate on modern-pauper and only play against friends, so I don't have any experience for top8 (or any other top decks). But to answer your question I would possibly remove [[Tilling Treefolk]] as I see it's only use in re-using [[Ash Barrens]] or getting lands back that you dredged into your graveyard.

+1
What about other creatures with madness like [[Basking Rootwalla]] or [[Brain Gorgers]]?

Guilds of Ravnica brought the "undergrowth" keyword: [[Hatchery Spider]], [[Kraul Foragers]] or [[Vigorspore Wurm]] could be of interest here. [[Spider Spawning]] could also be worth a look.

[[Hunger of the Nim]] could be an option. That's if you don't overdo it with the usage of [[Syndicate Trafficker]] or your opponent shoots all your artifacts.

2 [[Death Baron]] instead of 2 [[Cemetery Reaper]]? Nobody likes deathtouch and you still keep the ability to exile your opponents creatures.

There are some ways of making an angel deck fast and playable. One would be to use green defenders like [[Axebane Guardian]] and [[Overgrown Battlement]] to ramp while keeping your opponent at bay. Another would be to use less creatures and more control spells to keep your opponent from doing what he wants to do. The 3rd would be to use angels as finishers, have some cheap creatures that help you to survive early-game, and use the angels to strengthen your whole army. There are also some cheap(er)angels tough they normally start at cmc4:
https://www.mtgvault.com/cards/search/?q=angel&searchtype=type&mco=%26lt%3d&mc=4&l=Modern&ps=20

At the moment I would remove all cards that need a high number of creatures on the field or benefit from a high number of creatures entering (like Ajani's Welcome, Cathars' Crusade, and so on.

Last, a deck you've made should be made public so that others can see it. If you get lucky (a little bit of this is still needed) someone will find your deck and leave a comment so reminders in the forum shouln't be needed.

Greetings
Muktol

Questions what you want to achieve with the deck. For a mill-deck you got to few mill options, for a zombie deck (either aggro or control) you got to few zombies and support spells.

+1
War of the sparks brought us [[Courage in Crisis]] and [[Evolution Sage]], some really good card when you have some creatures with +1/+1 counters in them on the field.
Depending on your budget [[Doubling Season]] could be an option. [[Primal Vigor]] would be a little bit cheaper ($) but would cost the deck it's modern legality.

Another option would be to add a second colour. The best option here would be blue with access to some good proliferate and control spells.

Greetings
Muktol

The problem I see with [[Bushi Tenderfoot]] is that you need [[Field Marshal]] on the field to make him flip and make full use of him and even a simple 2/2 creature will prevent that from happen. [[Student of Warfare]] "only" needs mana to activate his ability.
There are some other cc1 soldiers that can be a pain in the ass for your opponent:
[[Doomed Traveler]]...people HATE those flying tokens.
[[Hada Freeblade]]...can grow stronger with time
[[Loyal Sentry]]...spot removal in defence
[[Skymarcher Aspirant]]...flying with 10 or more permanents on the field (lands count toward this)

My own human deck is more a aggro-midrange using [[Thraben Doomsayer]] and [[Mentor of the Meek]] to generate card-advantage and power-up [[Champion of the Parish]].

+1

[[Student of Warfare]] could be a replacement for [[Bushi Tenderfoot]] tough he's a knight instead of a soldier.
[[Call to Serve]] is a great card to get a single, strong creature over your opponents defence.
[[Brave the Elements]] is at least sideboard material, especially against mono-coloured decks as creatures with protection can't be blocked by your opponent's creatures.

Greetings
Muktol

I think [[Bonesplitter]] is more a halberd than an axe, just a minor detail. [[Darksteel Axe]] could also be an idea.

I've missed the "OR COPY" part in Ral's triggered ability.

I would insert a short summary of the Oathbreaker deckbuilding rules, or at least the main differences from brawl/ commander (using a planeswalker and a spell as commander), in the Deck Description as this is a rather unknow game-variant.

Some suggestions that came to my mind later:
[[Echo Mage]], [[League Guildmage]], [[Swarm Intelligence]], [[The Mirari Conjecture]]

Sorry to say that this doesn't work:
Lets say you've played a [[Lightning Bolt]], copied it with a copied it with a [[Twincast]] and want to use [[Ral, Storm Conduit]]'s -2 ability on [[Twincast]].

From the complete rulebook (http://media.wizards.com/2018/downloads/MagicCompRules%2020180713.pdf):
306.5d Each planeswalker has a number of loyalty abilities, which are activated abilities with loyalty symbols in their costs. Loyalty abilities follow special rules: A player may activate a loyalty ability of a permanent he or she controls any time he or she has priority and the stack is empty during a main phase of his or her turn, but only if none of that permanent’s loyalty abilities have been activated that turn.
So you can only use planeswalker ability's when the stack is empty (like sorcery's).

Lets pretend for a moment that this would work nevertheless. The stack will look like this now:
Lets say you cast a [[Lightning Bolt]] and copy it with a [[Twincast]].
Stack (Top Down): [[Twincast]] -> [[Lightning Bolt]]
Now you use [[Ral, Storm Conduit]] ability to create a copy of [[Twincast]] and target the initial Twincast with it.
Stack: [[Twincast]] (Copy) -> [[Twincast]] (Original) -> [[Lightning Bolt]]
The copy resolves, targeting the original, creating a new copy
Stack: [[Twincast]] (Copy2) -> [[Twincast]] (Original) -> [[Lightning Bolt]]
The copy resolves again (and so on), targeting the original, creating a new copy
Stack: [[Twincast]] (Copy3) -> [[Twincast]] (Original) -> [[Lightning Bolt]]
To end this loop you have to target the innitial spell, [[Lightning Bolt]] in this case, and end up with basically 3 Bolts in the end.
Stack: [[Twincast]] (CopyX targeting Bolt now) -> [[Twincast]] (Original, targeting Bolt) -> [[Lightning Bolt]]

The last problem here is that instant/ sorcery's that are copied aren't cast and thus don't count toward storm counter or activate ability's of creatures like [[Guttersnipe]]:
706.10. To copy a spell, activated ability, or triggered ability means to put a copy of it onto the stack; a copy of a spell isn't cast and a copy of an activated ability isn't activated.

Greetings
Muktol

[[Ghostly Flicker]] and [[Conjurer's Closet]] come to my mind. If you want to add a Planeswalker then [[Venser, the Sojourner]] could be worth a look.