Discussion of third-tier monsters.

To be honest, I never found the Fire Shield to be a particularly great ability in any of the games. For it to work, you have to expose yourself to an attack... and in doing so, lose troops. And the damage from the shield will be quite small compared to the losses. Besides, in every battle, you try to move your troops away from attacks, maneuver them... by definition, you avoid the infamous hordes.
By the way, it was a great decision to test the Outrider, from which you can be resurrected, and the Vampire, which is immune to poison.