I see two hero skills which are clearly broken, and overpowered.

Queen Brynhildr: AOE stun. Every turn. Get Shayd's skill and mix it with Smoulder's. And you can use Shayd alongside too.

Saffron: Berserker Rage. It's the same skill as Pompey the Great but uses up morale. The damage dealt is insanely disproportionate to the hp lost. With a fighter rune and equipment setup, my Saffron can do 250k damage and lose 16k health (out of 90k).