Here's why:
Say Bethesda added a Destruction Damage Encantment, similar to the other offensive skills (one-handed, two-handed, archery), that scaled the same. Meaning, you could have an enchantment on a piece of gear that adds up to 40% extra damage. That seems fair, right?
Well, I have a mod that adds such an enchantment. I have 3 pieces of gear that add +40% destruction damage each, plus all damage enhancing perks, of course. With still one 40% enchanting slot available, here are my flame damage numbers:
Flames = 26 DPS
Firebolt = 82 Damage
Fireball = 132 Damage
Fire Rune = 165 Damage
Incinerate = 198 Damage
Firestorm = 330 Damage
Flame Cloak and Wall of Flames are unchanged for some reason.
Two single cast Incinerates do nearly 400 damage (not even dual cast). These numbers are insane, especially if you have ANY cost reduction gear (I have one piece that reduces cost by 25%) and perks. I've been playing on master, and it only takes a couple of seconds to obliterate any enemy other than the hardest dragons with Deadly Dragons installed. The game is almost a joke! And I still have the option of increasing the damage by another 40%! If I do that I may have to crank her up to Legendary. That's how powerful destruction would be with such a simple enchant. It HAD to be nerfed somehow.
Not sure what do do with this information, but there ya go...