The strongest AoE and survivability build for endgame content. Maximum ability range with upto 400% selfbuffed ability strenght. Very expensive build.

Helminth:
Replace Molt with [Rhino] Roar. Roar increases damage to everything you do, including Spores and Miasma.
If everything is fully buffed you get yourself a 120% damage increase as a solo player, even more with [Power Donation].

Focus school:
Madurai school for extra ability power, use it when about to refresh Roar.

Operator arcane:
Magus elevate, extra survivability for situations where you may get bursted down to low HP.

Archon shards:
Azure shard with HP regeneration for quality of life, one shard.
Crimson shard with duration until Roar and Toxic Lash feel good for you, personally I go with extra 30% duration.
Crimson shard with ability power, fill the rest of the slots with extra ability power.
Try to get all Tau infused shards.

Weapon synergies:
[Ignis] and [Nukor] with Galvanized mods work exceptionally well with this build.

Mod alternatives:
You can change [Cunning Drift] with [Primed Sure Footed] or [Power Drift], however I found that the extra range is by far the best in terms of overall damage.
You can change [Growing Power] with [Power Donation], however this requires all of your squad mates to have the same aura.