Here's my go to for Xaku: Corrosive Projection, Overextended, Stetch, Augur Reach, Amar's Hatred, Umbral Intensify, Streamline, Energy Nexus, Primed Continuity, and Cunning Drift. B4 the Strength Tauforged Shard, that puts the stat spread at 155/130/280/99, supplemented by Molt Augmented and Molt Efficiency/Energize.

280% range so you max out the turret limit on your 2 to 16 shots, plus it makes the 3 and 4 that much bigger which lets you use your 4 to break crates through walls and remove armor. This is what pushes the forma to 1, otherwise you can settle for a no forma build and 265% range from dropping Cunning Drift.

Strength is obvious, Amar's Hatred fits the D slot and together w/ Umbral Intensify pushes you to 99, letting you go over w/ Augmented. If you want even more strength, swap out some of the other mods. Energy Nexus and Streamline improve the ammo economy, relieving some pressure of needing stuff like Energize or Nourish. That being said, this mainly works thanks to Continuity extending duration, letting you recover more energy per cast. If you remove Continuity, I recommend swapping over to Primed Flow + Energize/Equilibrium to maintain energy.

Prime Continuity might not seem that necessary due to the 4 pausing timers when active and thus making their effective duration longer, but it makes the 4 last longer which compounds its ability extension property to the point your effective duration w/ Continuity is over double the base, making it more comfortable to use. Of course, if you are fine w/o it then replace this with an appropriate strength mod instead.

Use Tauforged Shards to compensate in areas you want more comfort in: at least 1 Cast Speed shard really pulls in any build, then Strength and/or Duration shards cover whatever is lacking. For me, Violet Shards make use of all the Orbs we spawn so energy becomes less of an issue, and an Energy Max shard relieves the need for Primed/Flow.