The Thunder Hammer perk "Patience Rewarded", which Restores 1 Armour Segment after a fully prepared Aftershock (I'm assuming kill here, not specified) while below 30% HP. The issue isn't the charge time of Aftershock per se. You can stun something long enough to charge one. The problem is that while you are doing that, everything that is not stunned and shooting at you WILL kill you. Specially true at the higher difficulties.

The perk itself is useless, and on top of that, Assault lacks a reliable way to restore contested HP, like the Bulwark does. You can try to pull off a ground pound, or shoot something and see if you can shave some of it back. Unfortunately, this is often not reliable, as the machine spirit in the jump pack is spiteful and will refuse to engage for unknown reasons even while both charges are available. I propose replacing the perk in its entirety, with something similar to "Power Restoration" from the Power Sword. Power Restoration Restores 100% more Contested Health while in Power Style.

This little change will make Assault a less likely doormat.

Not a skill issue on Ruthless.