Compare to just charging up a fireball in each hand when we talk magicka consumption and damage!?

It's very magicka inefficient thanks to Bethesda's oversight, IMO.

I say yes if only you also get the impact perk as well alone nope.

I felt like there was a very small window of time when the extra damage from dual casting made the difference between surviving and failing. However, this phase quickly passed as my PC leveled. In hindsight, I don't think it was such a critical, strategic issue. You'll end up dual casting sooner or later so you might as well invest the perks early in the game and reap the rewards as soon as you can.