Hi all,
I went through the patch notes and thought it would be useful to write up all the notes that I think will impact the Infernalist (and more specifically my Arsonist build). Below you find my summary.
Atlas Updates
The Deadly Evolution Atlas Keystone has been replaced by a new Keystone called Ecological Shift which causes your Maps to have 40% more chance to contain Random Extra Content, and 20% less number of Monster Packs in your Maps.
Impacts modifiers on Rare and Unique monsters which in turn impacts drops of rare and unique items. This is completely removed and replaced by 40% chance to contain random extra content (I assume new Exile encounters etc) and 20% less number of Monster Packs.
The Crumbling Walls Atlas Notable Passive now has 10% chance for an additional Breach (previously 15%), 3% chance for three additional Breaches (previously 5%) and 1% chance for ten additional Breaches (previously 2%).
Significant decrease in the chance to get extra Breaches in maps. I found Breaches to be 1 of the more enjoyable end game events to encounter so I am sad to see this change.
The Frantic Invasion Atlas Notable Passive now has 50% increased Quantity of Breach Splinters dropped by Breach Monsters in your Maps (previously 75%).
As mentioned in Crumbling Walls (the line item above this one), I think any reduction in the Breaches approach is a bit of a loss to the game. I guess this translate to requiring to run more breaches in maps before you can get a breach stone and try the boss. Maybe this one is not too bad.
The Ominous Portents Atlas Notable Passive now causes Ritual Favour in your Maps to have 100% increased chance to be Omens (previously 50%).
This is fine, there will clearly be a bigger emphasis on the Omen currency in Dawn of the Hunt.
The Rising Pyre Atlas Notable Passive now has Breaches in your Maps have 25% increased Monster Density (previously 40%).
I really enjoyed the intensity of Breaches so I am sad to see they reduced this. It might still be intense because of dmg reduction and stronger monsters.. I will need to test this in the release.
Player Changes
Critical Weakness stacks now track duration individually, rather than refreshing the duration of all stacks when a new stack is gained.
This will impact Eye of Winter. I am currently not using this as I replaced this gem with Blink.
Revivable Minions now spawn with their skills on cooldown. This only applies to newly summoned minions, not Minions that have just revived.
This doesn’t have an immediate effect on my build.
Persistent minions granted by ascendancy passive skills will now automatically be summoned when you allocate the passive for the first time.
This impact the Infernal Hound. No major impact.
Infernalist
There are more changes to the Infernalist Ascendancies, I just note those that impact my current build
The Loyal Hellhound Ascendancy Passive Skill no longer causes 20% of Damage from Hits to be taken from your Hellhound’s Life before you.
This takes away the extra damage mitigation that the Infernal Hound provide 
Skill Changes
Adjusted Minion Damage and Life scaling. General Damage and Life is the same early game, but lower than before at higher levels, especially past Gem level 20+.
This means less damage and quicker minion deaths in end-game.
Adjusted the target Life Threshold for Skeletal Arsonist’s Explosive Demise Skill accordingly with the Life scaling changes.
I believe this one is related to the scaling of life. With less life I guess the moment an Arsonist can be used for Explosive Demise is lowered.
Adjusted Skeletal Cleric’s Heal Life scaling accordingly.
Healing is adjusted to lower life pools of minions.
Blink is now a Travel Skill
Unclear exactly what this will mean.
Direct Minions now has a 0.5 second cooldown.
I assume this is the skill that allows you to move minions (by using the ~ key). Not something I use a lot but it does have a cooldown now.
Eye of Winter now gains 75% of damage as damage of the corresponding Type when passing over an Elemental Ground Effect (previously 50%). The Skill also no longer incorrectly states the Projectile applies the passed over-ground effect to nearby Enemies.
I am currently not using the Eye of Winter skill but useful to have this in the overview anyway.
Flame Wall now causes projectiles which pass through the wall to deal 33 to 48 Added Fire Damage at gem level 20 (previously 64 to 91), while the Gem level 1 values are unchanged. More significant reductions have been made past Gem level 20.
This is basically the killer of my Arsonist build. I don’t think this will be a viable build in Dawn of the Hunt.
Flammability now causes Cursed enemies to have -25% to Fire Resistance at Gem level 7 (previously -32%), scaling up to -29% at Gem level 20 (previously -36%).
Reduced curse impact
Grim Feast can no longer be engraved in the Gemcutting menu. Existing Grim Feast Gems have been disabled, we aim to rework Grim Feast in the coming future.
This is another big one, Grim Feast is completely taken out of the game for now
Improved Skeletal Cleric behaviour to reduce cases where they would run at enemies and attempt to attack them.
Bug fix.
Pain Offering’s Aura now grants Minions 28-58% increased Damage at gem levels 5-20, rather than 29-44% more Damage. The Aura also now grants Minions 22-58% increased Attack and Cast Speed at Gem levels 5-20 (previously 30% at all levels).
This is actually an improvement from a damage and attack/cast speed perspective. Pain Offering for the win!
Raging Spirits now has a Spirit Duration of 5 seconds (previously 4), and a Maximum 2 Spirits summoned per Spell Cast (previously 5). The description of Raging Spirits has also been updated to make more clear that triggered spells will not summon spirits.
This means spamming Flame Wall like crazy, needing 5 Flame Walls to get a full set of Raging Spirits… 
Improved the performance of spawning very high amounts of Raging Spirits. If you spawn a large number of Spirits at the same time, the spawning of them is now spread out over a short duration.
It feels they killed the synergy of Arsonist/Flame-Wall/Raging-Spirits build with this update. This change just further reduces the viability of Raging Spirits. The question here is, what is “a short duration”? 10 millisecond, a second, 2 seconds?
Skeletal Arsonist’s Explosive Demise Skill deals additional Fire Damage equal to 12% of Minion’s maximum Life (previously 15%), and now has 2.4 metres Explosion Radius (previously 2 metres).
Further reduction of damage for Arsonist…
Skeletal Warrior can no longer be engraved in the Gemcutting menu, as it was only provided as a stop-gap until this functionality was implemented. Existing copies of the Skeletal Warrior skill gem have been turned into Skeletal Sniper gems. The Skeletal Warrior skill granted by some sceptres now allows you to summon additional skeletons by reserving spirit, in addition to the two free skeletons it grants automatically.
This makes sense.
Support Changes
Feeding Frenzy and Meat Shield can no longer support Minions which are undamageable.
Feeding Frenzy is okay as I was using this on my Arsonists. Meat Shield I was using on Pain Offering, curious if this still works (I am under the impression Offerings are damageable, but could be wrong).
Magnified Effect now has a 130% Cost Multiplier (previously 120%), and causes Supported Skills to have 30% more Area of Effect (previously 40%).
I am using this on Flammability, so it is becoming more expensive and less area of effect…
Meat Shield Support now grants Minions from Supported Skills take 35% less Damage, instead of granting them 50% more maximum Life.
This doesn’t feel the same but needs to be tested.
Scattershot Support now has Supported Skills deal 35% less Damage (previously 20%).
This one sucks as this was a key support for my Arsonists.
Strip Away now causes Exposure applied by Supported Skills to have 20% increased Effect (previously 30%).
Used this on my Infernal Hound…
Unique Item Changes
The Ingenuity Unique Belt no longer has 40-80% increased Bonuses gained from Equipped Rings. Instead, it now has 20-30% increased bonuses gained from Equipped Left Ring, and 20-30% increased bonuses gained from Equipped Right Ring. It also now has +1-2 Charm Slots, -20-20% increased Charm Charges Gained, and -10-10 reduced Charm Charges Used. Existing versions of this item are unaffected by these changes.
They nerfed it to 40-60% with charm effects
Item Changes
Sceptres can now only roll up to +4 to Level of all Minion Skills (previously +5). Existing items are unaffected.
This really sucks..
Sceptres can now only roll up to 80% increased Presence Area of Effect (previously 30%). A Divine Orb can be used on existing items to obtain these new values.
I assume this means what the range that you are considered near minions.
This is the list of changes that will impact my current build if I was planning to use the same build in Dawn of the Hunt. I might actually switch to a Sniper or Frost Mage Build consideren many of the mechanics are impacted.
Let me know what you think about the details around Dawn of the Hunt 