The build is meant for 5x3 / 6x3 tridolon speedrun tempo.
*Assuming you already know the roles for these specific run.
If you don't have the exact same things, just improvise it.
Eidolon scream duration is about ±3s (+wave travel time).
So harrow's duration ranging from 70% - 95% (4.2s - 5.7s invulnerability / 8.4s - 11.4s critical chance) should be fine.
Though, ideally i'd recommend to use the highest possible of that duration range so it can cover up the most of buff & invulnerability duration without interfering with your next cast.
Arcanes & Companion
• Combination of Arcane Energize & [Sahasa Kubrow]'s [Dig] to reduce energy pad consumption.
• or [Wyrm] with [Negate] mod could prevent some potential staggers, knockdown, or energy drain.
• Arcane [Guardian] for a bit of survivability.
You should consult this with your squadmates. You'll only want 3 [Corrosive Projection] & 3 [Coaction Drift] to strip the armor as much as possible without fully removing their entire trait. So you can still keep that bonus 75% radiation damage with the least damage reduction.