"Blackjack" Blade Vortex Archmage IndiScion - 6.5K+ Life, 3 mil Shaper DPS on a budget!

With the changes to brands and the Archmage support gem in 3.11, our build is hit obscenely hard with the nerf hammer; we lose ~20% of our damage.
Oh, that was it.
While I would never recommend an Indigon build as leaguestart, this build should still be powerful enough to take on most if not all endgame content, and will be the only Archmage Indigon build strong enough to do so (since the change to Brand Recall kills using Indigon on the Brand version of this build).
If you decide to roll this, enjoy!

You’re gonna need mana. Oh boy. A LOT of mana.
Our passive tree is giving us around 300% increased maximum mana, so added flat mana and %max mana are pretty much equally as good at this point. Remember, the sweet spot is between 5606 mana and 6541 mana; any less or more, and most of this build goes out the window. This puts me in the unfortunate position (based on the amount of ranges of mana one could acquire from even the unique gear in this build) of simply telling you where I think it’s best to pick it up: your final gearlist could look radically different to any other player using this build, and while it’s a large challenge, I also think it’s a fun part of making this build work. However, I reckon (though haven’t tested) that with my passive tree and jewels, just the added maximum mana craft on all your rare gear might be enough to get there on its own!

Vaal Blade Vortex – Archmage – Concentrated Effect – Unleash – Increased Duration – Elemental Focus
While this gem setup doesn’t give us the highest damage at first glance, it drives our mana cost to a specific amount for the maximum mana of this build. It also provides significant utility in minimizing the number of casts required to maintain maximum Blade Vortex stacks. You could use Awakened Unleash, but it only increases the damage through its slightly higher Quality stat of increased spell damage; Unleash Support’s “Supported Skills deal X% less Damage when Reoccurring” doesn’t affect Blade Vortex, and we have an artificial cooldown time of 4 seconds that is far in excess of the time it takes for Seals to recharge. Blade Vortex’s base damage itself only provides 3% of our final damage, so a 20/20 Vaal Blade Vortex was is more than sufficient for our needs. Keep a gem-swap Increased Area of Effect support on you, because it has the same Mana Cost Multiplier as Concentrated Effect Support, allowing us to seamlessly switch between better AoE for clear and more damage.
Wave of Conviction – Curse on Hit Support – Conductivity – Inspiration Support/Blood Magic Support
This is our best support spell, shredding a maximum of 70% elemental resistance towards Lightning Damage, and still providing a significant damage increase versus curse and debuff resistant bosses like the Shaper. Depending on your final mana cost of your Blade Vortex you can use Inspiration Support to make sure you never spend more than 1399 mana every 4 seconds, or Blood Magic Support so you can spam to your heart’s content (at some risk of doing your enemy’s work for them).
Vaal Righteous Fire – (Empower Support)
Righteous Fire grants us a significant more multiplier to our damage at the cost of health (and mana thanks to MoM and The Agnostic) per second. With our decent fire resistance, potentially the reduction from The Wise Oak, and our Mana Flask’s disgustingly large regeneration effect, we can happily sacrifice a small portion of our regeneration to nearly double our DPS with Vaal Righteous Fire and its less-blood-soaked cousin. You can use Empower Support if you have L O A D S A M O N E Y, and don’t decide to roll an unset ring to slot Vaal RF into, or you can skip both (because it's just 1-2% more spell damage).
Precision, Clarity
Precision and Clarity are here because they allow the use of specific Watcher's Eye mods we really benefit from, like Increased Mana Recovery Rate while Affected by Clarity and 1 Flask Charge Gained on Critical Strike while Affected by Precision. They also allow us to precisely tune our max mana, since they reserve a flat amount of mana instead of a % amount. Don't use them at any level above level 1 unless you achieve a maximum mana that would otherwise break the build (over 6541 maximum unreserved mana).There's likely some shenanigan in here you could pull with Vaal Clarity and dumping a huge amount of free spells during the duration, but for the life of me I can't think why.
Tempest Shield - Blood Magic
We don't have Acrobatics, so any block percentage is more and better defensive layering. Blood magic makes it so we don't accidentally break our build by casting it at an inopportune time, and our good duration from the passive tree ensures we don't have to cast it often, so it's no skin off our back.
Cast When Damage Taken – Steelskin – Summon Chaos Golem
A simple defensive trigger will save our asses more times than you can count. Try to aim for Level 11 CWDT and level 16 Steelskin, which just feels the best, since often times once you’ve triggered a level 20 CWDT you’re already dead. You can also use Steelskin and Second Wind, if you prefer to use your guard skills yourself, but this will take a lot more expertise and attention (but prevent a much higher amount of damage). If you self-cast, you shouldn’t have to worry about spending too much mana, but even still you may want to consider using Blood Magic Support as well (with all the hilarious implications of spending health to cast guard skills). This can also trigger a level 13 Chaos Golem, who helps with incoming physical damage a bit. He’s nice.
Shield Charge – Blood Magic Support – Fortify Support – (Culling Strike Support or Faster Attack Support)
Of course, a movement ability of some kind is really good, and Shield Charge is one of the best ways to get fortify on a ranged character! You can use Faster Attacks Support for even more speed, or you can use Culling Strike for finishing off bosses, but remember to socket Blood Magic Support or you will cry when you accidently spend too much mana during a big fight and lose 4 seconds of DPS.

Fevered Mind is a jewel that was recently nerfed (likely in response to the release of Archmage Support) to grant 20-30% spell damage and 50% increased mana cost of spells, from 100%. What Fevered Mind effectively does is reduce the total maximum mana required to spend enough mana with a single cast of Blade Vortex; for instance, since we need to spend between roughly 1200 and 1400 mana to trigger our Indigon 6 times and hit close to max mana efficiency, if our maximum mana is too low, then ~21% of our mana bar won't spend enough mana. Fevered Mind means instead our first cast spends 30% of our mana bar with one jewel, so we can have much less maximum mana and still spend between 1200-1400 mana per cast.
This opens the door to even more 'budget' versions of the build, or versions that scale spell damage in other ways, but it also reduces the power of Archmage Support (since our total mana costs have decreased with our maximum mana pool). In addition, even more ugly math rears its head, but one can generalise it to say each Fevered Mind you use reduces the number of Indigon Triggers you need to maximise your mana cost by 1 (the 50% on the jewel replaces one trigger of 60% on the helmet), and thus each one drastically reduces the maximum mana required (1 Fevered Mind Jewel hits peak efficiency with a Blade Vortex at ~3600 total mana and 1155 mana cost, and 2 Fevered Minds push the total mana you need down to ~2200, at significant impact to the damage supplied by Archmage Support.