Trinity Firestorm Stormweaver

Note this is not a completely fleshed out character, just a general idea for making firestorm playable.

Firestorm now consumes all 3 elemental infusions to gain extra bolts and deal cold and lightning damage. However, generating enough infusions can be difficult.

Orb of Storms generates a lightning infusion when it expires. Use Orb of Storms with Overabundance I and Compressed Duration II supports, as well as all the reduced duration nodes on the tree to get a 1.38 second orb duration. This will make generating infusions as simple as casting orb of storms and waiting for it to expire a second later. Combined with Elemental Equilibrium keystone, we can generate all 3 infusion types for firestorm.

Firestorm also has a limit of 1 by default. We get an additional limit from Stormweaver's Multiplying Squalls node, and another from Idol of Uldurn amulet. This lines up perfectly with the new lineage support Zarokh's Refrain, which allows our spell to repeat twice but gains a 5 second cooldown. So we can cast once and drop all 3 firestorms at the same time.

Since we deal a lot of hits of all 3 element types, we use Trinity to gain a ton of extra elemental damage. However, firestorm does more fire hits than the other two elements. To balance this out we use Archmage to gain damage as extra lightning based on our mana. This allows orb of storms to generate lightning resonance for trinity. Then we use Embitter support on our Elemental Storm (from the Stormweaver ascendancy) to convert damage as extra lightning into cold and generate cold resonance. This gives us good uptime on full trinity buffs.