[2.3] Elementalist Voltaxic Spark Really good high map clear speed+viability (t13+) and good life

So first off to kick things off we'll be going over the cost of this build. The build is very cheap with the drop in price of Voltaxic Rift creeping around 5 chaos orbs. Drillnecks go for about 1 chaos. However the main dps boost in this build comes from the flask Vessel of the Vinktar [+Spell Damage variant] which goes for around 30 chaos, and an Atziri's Promise, going for one chaos.
(Note: A flask of Grounding (SHOCK IMMUNITY) is absolutely required. Shock increases damage taken by 50%. I use an Alchemist's Quicksilver Flask of Grounding. You need it on a flask that won't expire due to life/mana pool.) Not only that, but I also added a Lightning Coil (5 chaos) because I'm able to achieve high resistances without my chest piece. It helps a lot with viability to end game maps by allowing you to tank that one hit or perhaps just add damage to your kit through Paragon. For my gloves I use a Winds of Change, another 1-5 chaos, it is best in slot
due to projectile damage mod multiplying the initial hit and the poison damage. For my helmet, boots, and accessories, I just use tri-res pieces with life. For boots you'll want 30% movespeed and preferrably the enchantment for health and mana leech, and for your belt you'll want around 400 armour.

I was able to achieve 70k solo DPS with Vaal Haste, Elemental Overload procced, and Pendelum of Destruction. I have about 28k dps, and with Pendelum I have 33k dps. This of course takes double golem, Herald of Thunder, and Wrath buffs into account. DPS tooltip also doesn't consider poison damage. This is also with a non-20 quality Void manipulation, just a level 19 0quality.

I'd say this build is somewhat viable in hardcore, although it might require some adjustments that might not make the build what it is. For example, you might want to switch Wrath with Arctic Armour, although you'll be losing a big portion of your damage. Although not recommended, if you want you could switch Lightning Coil with Belly of the Beast, in order to add that extra bit of health against
Atziri or Malachai. The damage is what makes the build. So for hardcore you might just want to go one of the top builds for that mode.

I was able to successfully run tier 14 maps deathless, so I'm assuming t15 and beyond just require good map mods and good play mechanically. I have footage in my video of end game map running, so you can just watch that and see for yourself.

This build runs bosses the best with Vaal Spark and flask charges up. I've run boss fights where they weren't able to land anything on me simply because of the knockback from Winds of Change plus my DPS just being so high. In the video you can see I melt a tier 14 Conservatory Vaal with the mechanic I spoke of. Trash mobs are very easily dealt with, probably the strength of a Spark build. Now after the nerf, you can't really kill things offscreen like you were able to before, but with Vessel of the Vinktar and the introduction of the fourth ascendancy point, this build is extremely strong when used in conjunction with the leech obtained from the mentioned flasks and the elementalist node Paragon, which adds another layer of tankiness.

For map mods, here's a list of mods you want to avoid.

Bad:
More Life + Maximum Boss Life : You'll lose a big portion of your poison damage due to the way damage works in this game. You'll also run out of
your flask pool, might run out of mana, and have something bad happen to you.

Chilling Ground: Really painful to run this mod when combined with mods that make the map seem plausible. Your cast speed is heavily reduced and therefore
you might get a surprise from someone like Daresso.

Hexproof/Avoid Status Ailments: You won't be able to apply Herald of Thunder's Curse on Hit Warlord's Mark since it requires you to kill a shocked enemy to proc.
You have a decent amount of leech from your flasks, but it's really annoying to have to press your mana flask every 3 casts to regain mana.

Heavy Damage + Reflect map: Reflect maps by itself are easily dealt with. When used with other difficult mods it's really just a surplus of damage that might lead to your death.

I think the rest of the map mods are easily dealt with if you are able to play them mechanically. Beyond maps are tedious but definitely manageable.

I rock Spark linked with Spell Echo, Controlled Destruction, Poison, Pierce, and for my six link I use Void Manipulation. Void Manipulation is better than Faster Projectiles, even after the nerf,
due to the double dipping of the more chaos damage modifier with poison.

For Vaal Spark I use Spell Echo, Pierce, Poison, and Void Manipulation. For my six link I'd use Controlled Destruction.

It's especially important to 20 quality and vaal your gems for this build because it's mostly based on your gems.

On my gloves I use Herald of Thunder - Curse on Hit - Warlords mark - Summon lightning golem - Warlord's mark. This is because 3 blues on a str gear is easier to obtain than on an evasion piece.

On my helmet / boots I use a mix of Summon Chaos Golem - Flame Dash and put a blink arrow. On the other piece I use Cast when Damage Taken, Immortal Call, Wrath, and Vaal haste.

Link: Passive Tree
For my passive tree I go through the lightning damage side of Witch tree, following the left side to Elemental Overload, which allows you to build damage without building crit. I went more to life for the survivability of end-game maps towards the end of the build. So I took more life nodes to fill the area, followed by the chaos damage passives by the Atrophy passive [Important to note here that you shouldn't go chaos damage until you are using a voltaxic rift. Plus you might want to go the elemental damage nodes around the Elemental Focus nodable for more damage early]. Then I went to the Elemental Focus nodable, and it's good for the chance to avoid status ailments. Then I got more life nodes... Taking what good nodables I could. I went to the projectile damage area with pierce chance for a combined total of 100% pierce chance with the gem. Followed by that I went to Acrobatics for even more survivability since I'm benefitting off of it, since I'm building evasion instead of armour. Around level 100 I would build either Arrow Dancing or look for a jewel passive for more projectile damage/life nodes.