WAIT. You're paying 370 - 500 for a Volt Prime?! That's way overpriced, they should be like around 100.

Anyway, if you're looking into playing Valkyr, I have an endless Hysteria build, and a very expensive max power strength build. The first (endless Hysteria) uses the concepts that I listed above, and since Hysteria makes you invulnerable to damage and you get innate Life Strike, this idea basically means you can't die. Ever. Unless you run into a nullifier bubble and die from the debuff from Hysteria. However, Narrow Minded both increases Duration by a lot, and reduces the range to so low of a value that the likelihood of this happening is quite low. You also put on Primed Reach on your melee weapon to aid you in taking down the bubbles without actually stepping inside. Essentially, you're either invulnerable, or taking damage to health -> energy -> Hysteria once more. Then you can kill things fast enough to offset the 0.63 energy per second this build costs. It's almost 11 minutes worth of being invulnerable at max power. You have a few options with this build, Steel Fiber and Rage can be swapped out with Eternal War or Intensify, if you prefer. There's a bunch of weird math, but basically for channeling abilities you can reach 190% efficiency by using a maxed Fleeting Expertise, Streamline, and a maxed Continuity. Anything above a 57.5 duration just helps your Warcry.

However, I have an alternate build which is extremely powerful (I've reached 1.3 million points of damage at points with this build), but also extremely expensive to build. It sacrifices some efficiency to have max power strength, but the efficiency can still be offset by killing things. I think it's only about 6 minutes and a half's worth of invulnerability with max power, but hey, 1.3 million points of damage! Here's the build. This is the absolute most Power Strength you can attain on Valkyr without replacing Vitality for Intensify. It has a drain of .98 energy per second, but comes with a 25 second Warcry. Unfortunately, it costs a lot to build (you can probably tell), and it's the only build I've ever created where I state that you absolutely need Primed Continuity, Primed Flow, and Narrow Minded at maxed (or near) ranks in order to offset the negative efficiency from Blind Rage.

As a final note, duration affects channeling abilities' cost. I believe that every frame should at the very least use Redirection or Vitality - solely depending on your abilities to keep you alive is a surefire way to get yourself killed at some point. I also believe that Eternal War isn't all that useful, you don't need to keep it endlessly running when you can just recast it every once in awhile. I won't go into depth about modding your melee weapon for Hysteria, but basically crit weapons are best (20% crit chance or higher), and the new melee mods do not affect Hysteria, so don't use them. This was the best melee build I could come up with. I just use War as an example, it's my fav. And Cleaving Whirlwind with it because it's a beast. It's the most damage possible setup with your melee weapon possible for Hysteria, you could always swap out Molten Impact with Life Strike, but it's somewhat redundant.

I hope this helps, glad it's appreciated!