Should be the best build possible for Sepfahn. Trusting that Viral proc is better than the -17k DPS loss. ("new" meta apparently, Slash+Viral/Heat instead of Corrosive) DPS-wise it's interchangeable with Seekalla grip (staff), gaining +0.5 range.
Use either Exodia [Hunt] or Exodia Force, both seem good but there may not be enemies within the 6m radius of Exodia Force.
Remember to check Apply Conditionals.

Best (Diversified) Zaw Builds:
Balla, Dagger (110k DPS)
Cyath, Machete (88k DPS)
Dehtat, Polearm (120k DPS)
Dokrahm, Heavy Blade (120k DPS)
Kronsh, Machete (92k DPS)
Mewan, Sword (81k DPS)
Ooltha, Staff (86k DPS)
Plague Keewar, Scythe (163k DPS)
Plague Kripath, Rapier (126k DPS)
Rabvee, Hammer (108k DPS)
Sepfahn, Nikana (106k DPS)