Isn't "Dual Casting" the same thing as I were to just use Flame in one hand and Flame in the other "at the same time"? Seems like using these 2 spells at the same time consumes the SAME amount of magicka as I were to use them in "dual casting". Am I wrong?

Also...seems like it does the same amount of damage as well. Whether I'm "dual casting" or using them individually at the same time.

Am I error?

You are error.

Can you please elaborate?

I forget the exact math but it's something like

Casting one spell in one hand is 100% cost for 100% effect
Casting two spells with no dual casting is 200% cost for 200% effect
Dual casting a spell is 280% cost for 220% effect.

Outside of impact, dual casting a destruction spell is not only useless, it's detrimental.

I thought it was 25% more cost for 20% more effect (or 250% cost and 240% effect), doesn't really matter as it is still underwhelming compare to say one-hands straight +20% damage at no extra cost, which you can get 5 times. Impact tho is very worthwhile if you can land it on mobs that tend to move around a lot, less wasted magicka via missing, also you can stun lock dragons which is insane. Impact is the only thing that makes Destruction Dual casting at all worthwhile.

Thanks guys so much for the info! Much appreciated!