Baseline this build has 385% strength. We then use Empower (50%) and proc: [Growing Power] (25%), [Energy Conversion] (50%), [Power Drain] (50%), Sling Strength (40%), Molt [Vigor] (45%), Molt Augmented (60%) and Pax Bolt (30%). Thus ending up on 735% strength which gives a 366% roar buff.
I would suggest a zaw with exodia brave to try to keep up with the energy cost
WARNING: This build is a meme, you are much better off without the 2 extra umbral mods and having efficency and duration instead.
(Can be increased further with archon crystals to a theoretical 405% roar)