[2.1] Storm Call - a different approach

The 2.1 patch has made this build significantly stronger, without the need to adjust anything major. With the increased base AoE, and the reduced "increased AoE" on the tree might change the best class to shadow, simply because you get more damage on the starting nodes, and the scion starting point is somewhat weaker in general. Nevertheless, nothing major changes in the build, except the performance :)

Storm call has an inherently large dps, but it has a flaw - it has a 1,5+ second delay before it hits, usually making hard to aim it properly. Instead of using the usual solution, the "less duration" gem, i have decided to go all in into AOE increases. I mean, when each explosion covers half of the screen each, its really not hard to aim - just cover the whole screen with explosions! We are skipping the good old "concentrated effect" gem as well - it would just kill all the fun.
How will we actually do damage, then, without conc? The answer is crit. Storm call has a 6% base chance to crit, so with power charges up, we are aiming to have 50+ % crit chance. This means, of course, that we are shocking as well, making up for the fact that we are skipping the huge damage increase of conc.
On dangerous mobs/bosses, use Vaal storm call after you cleared the little guys - it does a ridicolous amount of single target damage if it crits.

In my case, it was fairly simple - I have decided to make a pure MoM build, with an actual big mana pool, most of it unreserved. Since we are planning on massing up huge amounts of mana anyway, the actual storm call cost is like a drop in the sea, and we will regen it up almost instantly anyway. I am sure that u can make it work with either blood magic, or EB + MoM + ZO, but I have no experience in those.

This build is glass cannon-ish, meaning that we dont have any actual lifesteal, and we generally rely on our ability to kill stuff before it kills us. This doesnt mean that we ignore the survival stats tho - I have almost 5k life, and 2k+ unreserved mana for MoM + Acro/Phase acro. This, coupled with some usual CwDT setup, and some evasion/block, usually proves to be sufficient.
Since the removal of thornflash, we only have to care for single target reflect mobs. They are a pain in the butt, but with our fairly high effective HP against reflect (phase acro helps a ton), they can be dealt with. Just pot up before and after them, or possibly use a resist flask. I do the former.

https://www.pathofexile.com/passive-skill-tree/AAAAAwAABAcEswVCBbUHHgdjCGcI9A5IES0RlhNxFbgYPBhWHNwgbiL0KPoqCyycMHEy0TWSOkI6WDrhPAU9X0GHQZZFR0WdRwZJUUt4TLNN41AwUlNTUlVLVcZYrl3yXqVewF8qYeJirGNDZJ1o8mpDbAtsjG0ZcFJ8S3yDf8aCx4PbhTKIWonTjDaNv48aj0aP-pMnkzqVLpYylnSXlZf0muCdqp_fogCmV6cIrrO0xbc-uJO9J8BUwGbC7Mhby73Q0ND11CPYvdvn3ajr5Ovu6_XvfPAf8NXyHfJF8uH56P4K_o8=

You might notice the lack of increased lightning damage/spell damage/elemental damage nodes. We will be getting those stats from our staff and jewels. Getting crit from the tree is better I think.
We also lack castspeed from the tree - we will make up for it with a faster casting gem. Getting castspeed from the tree is also inefficient i feel.
When we gain more levels, we will be getting our 2-pointer jewel sockets.

Weapon:

Pledge of hands. We really need the mana, the huge spell damage increase is amazing (and it is something we lack from the passive tree, making it even MORE amazing), and an additonal link.
Honorable mention to Divinarius - If you make this build with EB-ZO-MOM, you can totally use this, possibly 2 of them.

Chest armor:

Carcass jack fits the theme, the aoe increase is amazing, and, most of all, fun. If you use Divinarius, or just want to be tanky, possible to use other chests as well - like a Lightning coil.

Other uniques:

I use Maligaro's virtuosity, it's a huge damage increase. You can try Voidbringer as well, or any general gloves, really.

Other pieces: I use rares on my other slots. Focus on getting flat hp, flat mana(!), resists. Manaregen or crit is a bonus. Energy shield is kinda meh because Acro cuts it in half, but not totally wasted, since we have decent amount if int to scale it up somewhat.

Storm call:
Storm call - inc. aoe - lightning penetration - faster casting - added lightning damage - inc. crit multi
You DONT want to use conc. Kills all the fun. You should have enough damage anyway.

Vaal Storm call:
Vaal storm call - spell echo - increased duration - lightning penetration - increased critical strikes
Why increased critical strikes? Mostly, because if Vaal storm call crits, its damage is sufficient enough to kill the single monster anyway (and we use it for single target). No need for more overkill. And if it crits, its damage drops so low, that it doesnt seem to do anything.

Herald setup:
Herald of lightning - curse on hit - assassins mark
The usual power-charge generator setup. The actual damage that you get from assassins mark is amazing. You dont want to reserve any more mana, tho, so no wrath :(

Mobility:
Leap slam - faster attacks - fortify - increased aoe
You can use any mobility skill you want, flame dash or lightning warp is totally fine. I use leap slam, because, coupled with the AoE increases, it makes it easy to get fortify for free, pretty much. If you land anywhere near close to a monster, you will get the fortify. We also lack the usual cast speed increases from the tree, making lighting warp/flame dash relatively slow compared to usual.