Build for my Nikana Guide.

Primed Reach - Increases AOE so you hit further and hit more enemies, which helps build combo count quickly.
Blood Rush & Weeping Wounds - Scales with combo count.
Condition Overload - Provides insane scaling damage with status procs
Organ Shatter - Increases the damage of critical hits
Berserker - Highest Attack Speed boost, can be Primed Fury instead if you prefer the consistency.
Primed Fever Strike - Best elemental mod available to melee, builds into Corrosive.
Vicious - Cold mod of choice for Viral, bonus status is good

Zaws come with one free polarity of choice, so the build is technically only 2 forma.