I got Nidus about 2-3 weeks ago and instantly jumped into steel path endurance runs with him.
This is the build I settled on. It's not perfect by any means but will easily take you to about 2 hours on steel path before you have to leave.
Before I explain [Nidus] and how to use him, I want to say 2 things.
1. this build is strictly for solo play
2. life support will need to be monitored so that you can keep going

PSA: You do not need max rank mods on any frame. At some point you may want to just to maximize survivability, nuking, CC, etc., but you could never rank them up to max and be perfectly fine doing literally anything in this game.

The arcanes do not matter as I do not have any ranked up warframe arcanes.

Building [Nidus] is like a balancing act because ever stat affects his abilities differently.

FIRST, allow me to briefly explain his abilities

[Nidus]'s gameplay revolves around him building stacks through his 1 and

Passive: If [Nidus] dies with 15 or more stacks, he instead enters an invulnerability phase for 5s where he regains 50% health

1. Virulence
   [Nidus] strikes the ground sending a trail of infestation that he uses to build stacks

incomplete guide