Yes paralyze targets high HP first in my experience. I a MP game I play as MA atlantis now I managed to counter my enemies spamming of paralyze/soul slay/etc... with scattering some elephants around. Not one of my thugs have been targeted since, the elephants are targeted over and over even after being paralyzed. Should work with any high HP unit.
Aye I went back and checked. I have the misfortune of playing a nation where the sissy spell casters have more hit points than the guys swinging the swords. I will take the appropriate steps to protect them .