While I support your efforts to better balance the game, the true imbalance lies in attack speed. Player characters attack wicked fast, even with spells. Enemies attack godaweful slow, even with spells. If that imbance were corrected, you could normalize enemy HP, HD, Loot, abilities and **** near everything else in the game.
As far as firewall goes, the spell itself isn't broken so much as the AI. In general the DDO AI is outstanding, but having enemies ignore danger was a miss. Correcting that would go a long way toward balance without having widespread (likely unintended) consequences.
In short, game balance is best achieved when the enemies have similar capability of the player character. That simple.