[Umbral Intensify] (R9) + [Augur Secrets] + [Corrosive Projection] gives you the exact right amount of Ability Strength to 100% Strip Armor with a single cast of Tharros Strike. This is really the only thing I feel is "Required" to play him. You can go more Strength if you want but I didn't find it necessary.

[Primed Continuity] + [Augur Message] for more Duration on his 1, 3 & 4

[Primed Flow] to offset the high Energy cost of Final Stand

[Stretch] for a bit more Range.

[Adaptation] (R8) to make his shields tanky, if you want to take it to R10 you will need another Forma and I personally don't think R10 is worth.

[Boreal's Hatred] for Passive and Synergy with the 4. Can Forma for [Primed Vigor] if you want more Health.

[Augur Message] is a "Flex" spot. [Augur Accord] and [Augur Reach] are options if you don't want another Forma. Can be whatever you want here but anything other than an Augur mod would require more Forma.

I know people are complaining about Low Health on Stynax but if you want to take him into Steel Path, I'd suggest running a [Huras Kubrow] for 100% Invisibility from [Stalk] instead of trying to make a Shield Frame lose synergies by adding HP. As long as you don't Shoot a weapon or go inactive, you can always be invisible with [Stalk].

I've been considering replacing his Axion Javalin with Pull from [Mag]. It just feels better while the grouping isn't quite as strong.