I like both lists (@BurningForce, @Amicdeep) and each one has it's pros and cons.
Now that Jace is rampant again, it should be mandatory to have any way to get rid of it. I think flash creatures are key in that so Archangel Avacyn and Restoration Angel are good ways to accomplish it. THe only problem with Avacyn is that it can clean your board also so you have to be very smart knowing when to cast her.
Probably wants some more lifegain support (similarly to Crested Sunmare) in a soul-sisters hybrid of the deck, probably 4x Auriok Champion for starters.
This is what I've been playing recently... I like less borderposts, so I am only playing the posts that support my splash. I hate getting land destructed by the Affinity hate in most sideboards... With this configuration, I am less susceptible to those hate cards and if they bring in artifact hate against me they are only able to target my four borderposts so its probably now a bad sideboard plan for my opposition. Weathered Wayfarer can search to get Azorius Chancery, which almost acts as another land and reduces my lands in play, but I am running 20 lands and a virtual 25 with the borderposts and the chancery. But we get opportunities to ramp with Knight of White Orchid and Weathered Wayfarer. But I also am finding more utility land like Moorland Haunt to help me in long games and a 3/3 flyer is nothing to sneeze at in a deck like this, sometimes those Moorland Haunt tokens are even bigger.
But I've switched into a token subtheme with a little bit of Knight matters added to the subtheme that works well with Benalia, KoWO, and Gideon and Riftmarked Knight that might be interesting out of the sideboard in some Black matchups. Leyline of the Meek is always relevant to my deck and the singleton Leyline of Sanctity is never in doubles anymore, but I actually have an extra opportunity to get a Leyline in play on Turn 1 because I am running one more Leyline than most devotion decks.
Balancing a midranged deck in Modern is hard. Its hard to have a decent game against everything, but this deck can do powerful things. Tokens are often like card advantage.
Been playing Mono White Devotion for about 1 year now in different types of builds. One card that I have used and won many games with is Entreat the Angels. I like this card for its miracle cost. I have been running 4 in my deck.
The addition of an efficient removal spell like On Thin Ice really helps the deck's early game.
It is yet another deck that can utilize the Karn + Lattice combo to close out games with the mana it can produce.
Ugin never seemed great here as the minus ability is usually not good here so I'd probably want something else here instead.
Like: Gideon Jura or maybe Iona or Avacyn.
Another interesting choice here is Auriok Champion which is decent but the deck doesn't really flood the board with creatures so maybe Kitchen Finks would be better instead or maybe something like a Grand Abolisher or Tomik (to protect Nykthos).
I'd probably like Shalai in this deck as well even in the SB though it can be maindecked as well for more protection.
Serra the Benevolent can be pretty good in the deck, it is at least a Worship which can't be removed if you can keep her on the board for a turn.
I don't know if Gideon Blackblade deserves a slot in the deck but he can be considered as well.
id add to you analysis on Auriok Champion. because this was a competitive event its placed really well to hate really hard on hogaak, phoenix, burn and deathshadow
Now that Jace is rampant again, it should be mandatory to have any way to get rid of it. I think flash creatures are key in that so Archangel Avacyn and Restoration Angel are good ways to accomplish it. THe only problem with Avacyn is that it can clean your board also so you have to be very smart knowing when to cast her.
Also Evangel of Heliod and Anointed Procession are great in a devotion shell because they give you the game usually.
Also the blink effects are really nice in this deck so Cloudshift seems really good here also.
I think I would build the following list:
4 Knight of the White Orchid
4 Springjack Shepherd
1 Heliod, God of the Sun
1 Evangel of Heliod
2 Archangel Avacyn
1 Angel of Invention
1 Akroma, Angel of Fury
2 Restoration Angel
1 Legion's Landing
4 Runed Halo
3 Honor of the Pure
1 Spear of Heliod
4 Leyline of the meek
1 Cast Out
1 Worship
1 Anointed Procession
2 Fieldmist Borderpost
4 Wildfield Borderpost
Instants (9)
4 Path to Exile
1 Secure the Wastes
4 Cloudshift
Lands (18)
4 Nykthos, Shrine to Nyx
11 Plains
2 Shefet Dunes
1 Springjack Pasture
Still have to cut 5 cards But I don't know what to cut because everything seems pretty good in the list
But I've switched into a token subtheme with a little bit of Knight matters added to the subtheme that works well with Benalia, KoWO, and Gideon and Riftmarked Knight that might be interesting out of the sideboard in some Black matchups. Leyline of the Meek is always relevant to my deck and the singleton Leyline of Sanctity is never in doubles anymore, but I actually have an extra opportunity to get a Leyline in play on Turn 1 because I am running one more Leyline than most devotion decks.
Balancing a midranged deck in Modern is hard. Its hard to have a decent game against everything, but this deck can do powerful things. Tokens are often like card advantage.
2 Elesh Norn, Grand Cenobite
4 Knight of the White Orchid
3 Walking Ballista
4 Weathered Wayfarer
2 Elspeth, Sun's Champion
2 Gideon, Ally of Zendikar
4 Fieldmist Borderpost
1 Legion's Landing
2 History of Benalia
1 Leyline of Sanctity
4 Leyline of the Meek
1 Nevermore
1 Oblivion Ring
1 Detention Sphere
4 Path to Exile
1 Quarantine Field
1 Rise of the Hobgoblins
2 Secure the Wastes
1 Island
2 Hallowed Fountain
1 Azorious Chancery
1 Moorland Haunt
4 Nykthos, Shrine to Nyx
10 Plains
1 Riftmarked Knight
1 Devout Lightcaster
1 Grafdigger's Cage
1 Entreat the Angels
1 Nevermore
1 Hangarback Walker
1 Quarantine Field
2 Rest in Peace
1 Azorius Charm
1 Tectonic Edge
1 Supreme Verdict
1 Day of Judgment
2 Wrath of God
https://www.mtggoldfish.com/archetype/modern-wug-89816
The addition of an efficient removal spell like On Thin Ice really helps the deck's early game.
It is yet another deck that can utilize the Karn + Lattice combo to close out games with the mana it can produce.
Ugin never seemed great here as the minus ability is usually not good here so I'd probably want something else here instead.
Like: Gideon Jura or maybe Iona or Avacyn.
Another interesting choice here is Auriok Champion which is decent but the deck doesn't really flood the board with creatures so maybe Kitchen Finks would be better instead or maybe something like a Grand Abolisher or Tomik (to protect Nykthos).
I'd probably like Shalai in this deck as well even in the SB though it can be maindecked as well for more protection.
Serra the Benevolent can be pretty good in the deck, it is at least a Worship which can't be removed if you can keep her on the board for a turn.
I don't know if Gideon Blackblade deserves a slot in the deck but he can be considered as well.
Competitive Decks
Devotion to the Lash B ----
Monkey Conservation WUGR ---- Dragon WorshipR