A lot could be said but I’ll keep it simple:
Keep the charge mechanic, but extend significantly it’s active period(change peril generation as required to balance)
The Void Blade special as it is now should activate only on a Heavy Attack, kills with this attack generate a Warp Charge.
On light attack, the charge should apply a fixed percentage damage increase and a cleave ability for a fixed time.
This will not wholly address the issues with Warp Charges that many have encountered, but would make the Force Sword a more viable weapon.