Please allow Heralds to be used with an empty main hand + shield off-hand (for concoctions)

I want to play a bleeding concoction build but not being able to use Herald skills completely kills it's ability to clear. I understand making Herald skills require a martial weapon is because they're meant to be used with attack builds, not spell builds, but concoctions are attacks and yet they cannot use Heralds.

I know Hollow Palm lets you use Heralds unarmed, but that requires both main and off-hand slots to be empty, meaning you can't use a shield which ultimately makes it a non-option.