Please read each detailed mod slot carefully which explains it all. As for having health at 6728 won't be a problem since this is a health regeneration build.

[Corrosive Projection]: Got nerfed but there is a better aura. Let us move on.

[Physique]: Maxium Health increased 90% health, not bad but doesn’t benefit for [Inaros] lasting longer in long end missions. It’s just increases health, nothing more please read the next mod.

[Rejuvenation]: Oh yes this mod. Specifically states +3 heal rate per second. Let me explain once he takes damage health regeneration from [Rejuvenation] and arcane grace kicks in. This is the most beneficial out of [Corrosive Projection] and [Physique]. We want [Inaros] to regenerate health to keep him alive during specific missions. CP and [Physique] doesn’t do that.

Note: Using [Steel Charge] you need a great melee like [Gram Prime] or a dagger with great setup if doing finishers. I have tested out my [Rakta Cernos] build and never failed me. Keep in mind you want to remain tanky though during missions like Defense and Survivals.

Note: [Energy Siphon] see Slot 7. But with [Rage] or [Hunter Adrenaline] he is able to gain energy based from damage to be added to his energy pool.

Exilus adapter slot can be used with other mods but I use [Coaction Drift] (+15% aura strength and effectiveness). So experiment with this slot that you feel comfortable using.

Slots 1,2, and 3: All three umbral mods are crucial for benefiting each other. Increase in Health, str, and armor with all three Umbral mods would be 6728 which is good.

Slot 4: [Adaptation] as it states When damaged: +10% resistance to that damage type for 20s and then stacks up to 90%. Types of damage include slash, puncture, impact, and so forth. Please max this mod out for full potential like the other mods mentioned in this build.

Slot 5 and Slot 6 are thinking outside the box for [Inaros Prime]. [Rage] or [Hunter Adrenaline] along with [Gladiator Finesse] or [Quick Thinking]. Now why would we use these mods. Let me break this down

[Rage] or [Hunter Adrenaline] converts damage on health to energy adding to his energy pool. Wham, Bam, thank you ma’am he has gained energy to his energy pool (see Slot 7). Now once [Inaros]' health gets down to a low point that is when [Gladiator Finesse] or [Quick Thinking] kicks in by draining energy to stop lethal damage. Read Slot 7 which [Primed Flow] will increase his energy pool tremendously.

Note 1: For those with hunter builds feel free to use [Hunter Adrenaline] mod to replace [Rage].

Note 2: [Quick Thinking] mod is an excellent choice. And so is [Gladiator Finesse] since that mod is part of a set. Just pick which one you are comfortable using.

Slot 7: [Primed Flow]. Why may you ask? Check out the cost of his abilities since this build isn’t using [Streamline]. The 425 energy pool allows [Inaros Prime] to not only cast abilities if need be. But with [Rage] or [Hunter Adrenaline] he is able to gain energy to his energy pool upon damage to health. And then [Gladiator Finesse] or [Quick Thinking] will pull from his energy pool to stop lethal damage. Keep in mind that [Gladiator Finesse] and [Quick Thinking] has a certain amount of efficiency so 125 energy pool won't be enough. Thus resulting in having a [Primed Flow].

Slot 8: [Gladiator Aegis], Primed Vigor, Gladiator Resolve, Primed Sure Footed, and other mods to experiment with that slot.

Arcanes: Grace and Guardian. Fury/Strike for using [Steel Charge] aura. With Grace and [Rejuvenation] his health regenerates quickly.

Final thoughts

[Inaros] doesn’t need around 9000 health as I have seen in other builds. To have over 9k of health on a Warframe like [Inaros] is just for show. He is a tank and needs health regeneration to last longer in specific activities. With this build I was able to regenerate health back and keep [Inaros] alive. If you have a HIGH eHP then how will you regenerate health quicker?

Example, I regenerated health quicker in a Arbitration Survival than an [Inaros] that had 9000 health. He left at the 60 min mark while my build lasted till the 70 min. I have tested this build out minus using an [Umbral Intensify]. Also I had dozens of players on console whom asked me for my build during missions like Arbitration.