Destruction increases the damage output of your magical attacks, so I think it's a must to have... but I think it's most important if you rely on fireball/firewall only for magic.
Nightbringer set is good, but Ufthing's armour is much better because of the many stat boosts + charm/enchantment possibilities it gives.
Your mage has strength 1... but then how did you manage to survive the fight with Stone... and how did you manage to kill Raze without a high level magic blast/fireball/firewall? You need to kill him very quickly and magic missile just doesn't cut it.
