[0.3] Hexblast Pathfinder - 200% rarity - 60% MS - slow/curse immune - clears all content

I am lower level, what points do you recommend to drop?

I wanted to make a build that makes good use of this iconic pathfinder ascendancy notable:
Contagious Contamination

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The most Damaging Poison on Enemies you Kill is Spread to other Enemies within 1.5 metres

Why is this difficult? Because Herald of Plague exists. For a measly 30 spirit you (and every other exile) have access to an almost strictly better version of your precious ascendancy notable, since the herald version also hinders and has a larger spreading range (depressing). However, it is meaningfully worse in one regard: it requires a martial weapon. So, we will be a spellcaster.
Good news, because another thing that I wanted to try out was Hexblast. Curses are interesting and the spell itself has extremely high base damage (4x Lightning Bolt). But it is clunky. There is no way around it: we have to cast a curse, wait, Hexblast. We plan to mitigate the clunkiness by casting as little as possible: AOE one-shot.

Because Hexblast does chaos damage, we can solve the AOE part with our ascendancy (if we actually one-shot the first thing that we poison).

To improve our one-shot potential we grab everything that gives a lot of stats for the trade-off conditional "enemy on full life", since we plan to only hit once anyway. The best of these things are related to crit (e.g. nodes on the tree, ambush support), which is not a good match for Hexblast as its base crit is quite low (7%). But we need to reliably crit, because once the enemy is no longer on full life, we will lose a lot of damage. For this reason we are going to use Sandstorm Visage, which adds flat crit%. We commit, no plan B.

Curse effect is also really strong. Poison has great innate synergy with curses because both despair and temporal chains scale poison damage. Making everything slower with temporal chains also gives us more opportunity to cast our two spells without getting interrupted. Since we want to scale curse effect anyway, it makes sense to add any useful curse. Lucky timing: they added a new support that gives +1 to curse limit (Atziri's Allure). Note that temporal chains also has synergy with Wither and Sandstorm Visage!

Back to Hexblast. Before we can cast it, half of the curse needs to expire. The first iteration of the build played around with reduced skill effect duration and support gems that lessened duration, but still, there were a few unfortunate anti-synergies. Firstly, we want a high curse skill level for the larger effect and the area, but that increases the duration. Secondly, our temporal chains makes the curse expire slower on enemies... It worked, but there were definite downsides. But again, we are in luck, there is a new support gem that applies the supported curse with a 3 second duration (Doedre's Undoing). This makes the build a whole lot simpler to put together. One small problem, this support gem does damage. For most builds this is never a bad thing, but we need our enemies in tip-top shape (Full Life). So, we add brutality support for its downside (no ele/chaos damage)!

I play 3 curses: Despair, Temporal Chains and Enfeeble. I use Despair as a long, self-cast curse with Hex Bloom. When self-cast the effect is much stronger and this is a very strong damage scaler (both hit and poison damage). It is not meant to be detonated but it can sometimes be detonated in boss fights. It is then a boon that it has a long duration as that is a more multiplier for Hexblast (skill gem quality).

Then one other curse you will decrease the duration of so you can detonate it with Hexblast and another can be applied with an aura using Blasphemy support. Because some monsters in POE are really fast, I prefer having Temporal Chains as aura with Blasphemy. You're slowing the enemy less, but you are slowing them faster and more reliably.

Atziri's Allure needs to support one of these gems. The boon of +1 to curse limit comes at the cost of curse reflection. But, it reflects the curse only when you cast it, so if you put it in Blasphemy you don't have to suffer that downside. Nevertheless, I am a big temporal chains fanboy. There are now great curse reduction runes (body armour) and some nodes on the passive tree so I slot it in Enfeeble and curse myself. Curse immunity is nice QoL but note that you need >100% curse reduction if you want to get rid of everything because of the notable "Impending Doom" on the tree.

They now made weapon swap instant, which is an amazing change. I liked it before but it just felt a little bad. This build makes great use of the two skill trees, with one that focuses on damage (crit, enemy full life, ...) and another on curse related effects. Because we have less Energy Shield on the Focus in our Hexblast weapon set (we want increased damage prefixes), we take a bit more defensive nodes to match our defenses in weapon set 2.

Otherwise, common nodes are defenses (evasion, ES), movement speed, mana cost efficiency (both curses and Hexblast are very mana hungry), jewels and stats.

The jewels are really specific as we need them to get to 100% chance to poison. One of them also needs to have recover %mana on kill. Also, take increased presence area of effect wherever you can get it (campaign, Sapphire jewel). It is important for both Wither and Sandstorm Visage. I also play one of the new Abyss jewels: the Amanamu one. It changes nodes on the tree we don't want to nodes we want even less, but it comes with a great keystone: 20% of hit damage prevented and taken as life loss over time. This improves our max hit and we care very little about damage over time. We grab the life flask ascendancy notable and Shavronne's belt that also applies the life recovery from our flask to our ES (double recovery!). Another thing we do to "increase" our max hit is to reduce blinded enemies' critical hit chance on the tree. Remember that we blind with Sandstorm Visage.

As luxury slots we take the movement speed ascendancy notables. These are just great QoL and it makes it (together with our curse immunity) that we don't need to read map modifiers anymore.

There are a lot more details that I can discuss but this was probably already way too much. I really enjoyed fine-tuning this build and I strongly recommend it, especially if you think the gameplay looks like something you'd enjoy and you don't mind pressing two buttons.

Curse limit is increased from 1 to 3 with Doedre's Damning (ring) and Atziri's Allure (support gem).

1. Temporal chains as aura on Blasphemy support.
2. Despair self cast to maximize effectivenes. Also range comes in handy to propagate poison waves. It does not need to be cast that often.
3. Enfeeble to detonate. This is supported with Doedre's Damning to decrease its duration to 3s. It is supported by Brutality to prevent it from doing damage so our Hexblast can still hit the enemy on Full Life (this is important!).

Atziri's Allure supports Enfeeble because we care the least about this curse. We mitigate the reflection with runes (body armour, 80% reduced curse effect), Inner Faith (25%, passive tree). Because of Impending Doom on the passive tree you will see your Enfeeble effect go from 0 to 6%, halfway through the curse duration, if you don't also allocate Curse Effect on Self (passive tree, 15%). This is worth the two nodes. Even though the 6% damage reduction is only on us half of the time at most, it is always present when we want to Hexblast.

You can slot in Atziri's Allure in Blasphemy and then you can use other runes in your body armour and don't need to jump through the curse reduction hoop. But imagine that you had runes you could slot in your body armour that would slow everyone around you? Wouldn't you want those? So I think it makes sense to have it on Enfeeble and jump like a good dog.

Boss
Circle boss in your presence to accumulate Wither (Buff) and Critical weakness (Sandstorm Visage) stacks. Cast Despair. Cast Mark. Cast Enfeeble a little before your despair is halfway though its expiration. Then Hexblast when the despair is at increased effect. You can check PoB and it will depend a little on your gear, but with 3-5 critical weakness stacks you should be guaranteed to crit.

You can Hexblast a second time to detonate the Despair as well but cool kids only blast once.

Map
Enfeeble - Hexblast everything. Try to aim as far in front of you as possible, that makes it feel less clunky. When monster density is high enough, just propagate your poison by casting Despair: Enfeeble - Hexblast - Despair (aimed a little further).

We make excellent use of weapon sets, a lot of it is straightforward but here are some small details:

Weapon set 1
Skill(s): Hexblast
Wand/Focus: damage oriented

Weapon set 2
Skill(s): Enfeeble, Despair
Wand: utility (cast speed, mana regeneration, ...)
Focus: utility, faster curse activation (important!), defenses

• Because Contagious Contamination is also poisoning while we are cursing in weapon set 2, some poison nodes are useful to have in both sets. All the poison notables (except the one in weapon set 1), are very important. I am assuming this is how it works based on the wording, please correct me if you know more.
• Because we can use the prefixes of our Curse Focus for defenses we have more ES on weapon set 2. We grab some more defense on the tree in weapon set 1 to compensate. This might be counterintuitive because 1) it is the offensive weapon set and 2) it's generally a bad idea to skim on defensive nodes in one of your weapon sets.
• Wither is only allocated in weapon set 2. Wither is important for bossing and we are waiting on Wither and Critical Weakness stacks in the Curse weapon set so no need to have it in both. This also might be counterintuitive because wither seems offensive and it is not in the offensive set.