If you don't have [Primed Sure Footed] swap it for [Handspring] and use a rank 6 [Adaptation] instead to reduce the forma cost to just 3.

300% efficiency lethal damage energy drain + 1850 armour + the damage reduction from [Adaptation] makes you very hard to kill.
You have enough efficiency for Bloodletting to instantly refill your energy bar to 100% with a single cast, and Gloom being up lets you instantly refill your HP to 100% with a single attack, meaning as long as you pay a little attention your HP and energy pools are infinite.

Gloom only costs a maximum of 3 energy per second to keep up indefinitely, you also have enough power strength for Seeking [Talons] to grant 100% slash chance.
I'm not an endurance runner, but this build routinely lets me last 2 hours + in steel path survival or disruption with zero effort. I've never bothered trying to see how long you can last until the massive amount of effective HP you have no longer matters, but for most players what it can already do is more than enough.

I also strongly recommend getting a rank 5 Arcane Nullifier for the times you get energy drained when you're not paying attention, it basically addresses the only weakness of this build, and it's one of the cheapest arcanes available.