Damn healers. Need advice. (Vikings: Wolves of Midgard)

How do you kill healers immune to instant death.
Faced with a giant, on which sits the rider a mage who heals him constantly. At the highest difficulty physically difficult to bring the health bar to zero. It seems that here-here will kill it again until the middle of restoring.
ZADOLBALI!!!
And so have top-end gear, and runes for crit use.