My current character is focusing on the mq, dlcs, companions, and the mages guild. The focus is on light armor, dual wielding, smithing, enchanting and conjuration. Would Restoration become a necessity later on?

Restoration is never a "necessity", but is always useful for almost any build.

I suppose I was really just curious if I should start using it as a backup. As of now I don't need it, but I'm worried that tougher enemies would chew me up. Since I am using light armor and no shield.

This. It's also got a lot of very handy perks.

Nah, smithing makes light armor better than heavy armor and dual wielding owns life. If anything just carry around a bunch of potions.

With this in mind should I start focusing sone effort into alchemy then?

As for the other replies so far I agree I am destroying everything in my path. I just don't want to back myself into a corner and turn into a dragon chew toy.

I love me some alchemy, so I say go for it. Poisons may become your best friend. And you may want to look into using tempered but unenchanted swords for dual wielding so you can take advantage of Elemental Fury.

Not needed, but usefull.

My Necrowarrior uses it, but she has no perk points in it. I might get to that some other time thanks to legendary skills.

Anyway, yeah it has saved her mystical ass plenty of times. It can still be usefull even if you have no perks in it.

Out of 30+ characters, only 1 has invested in that school of magic.

Well my character has been saved around 572 times cause of Restoration. Anyway you could say that light armor is stupid because you play only with heavy armor