Going to make a new character this weekend. My last character was a bit of a pain, I had an armor-less mage using conjuration and illusion as main skills. It got boring because before every enemy encounter I had to use the alteration armor spell to get some armor and summon a helper before I could start the fight. Alteration is pretty powerful but it gets annoying to keep refreshing the buffs (why can't they make the armor spells last 15 minutes or so?)

But that was a few patches ago, so with all the new patches I was thinking of a mage wearing light armor, destruction, archery and alchemy. Anyone played something similar, is it a fun and viable build? Maybe I'll use conjuration instead of destruction if that's better.

With my last pure mage I just stopped doing the shield spells altogether. I concentrated on Conjuration and Destruction. Playing on Adept my mage was able to survive nicely with 0 AR.

Use one handed, with a dagger hotkeyed, with Light armour, with enchantment for less magica costs for destruction(hands+helmet) Conjuration(Boots+chestpiece), and if you build up enchanting, do each piece 1 destruction cost less magica, and one conjuration cost less magica

Well I don't think it's enough, at least at Master level of difficulty. But if you're on PC, I recommend the mod Mighty Magic Skyrim. It adds scaling (and other good stuff), increasing both the strength and duration of such spells.

But if you can't or don't want to install mods, there's still one thing to note : with Conjuration and Illusion, you typically don't need any kind of armor.

I have a light armor paladin

Skill:
One hand
Block
Archery
Light armor
Restoration
Alteration

The combination can get me close to max armor rate without much smithing and enchanting

Thanks for the mod suggestion, but on Master difficulty you need armor when fighting strong enemies.

I mean you can make them fight together, or calm them if they get too close, and later become invisible. And your summoned creature are there to tank damage.
Using those skills (just like sneak+bow, which level up so fast), you'll have trouble leveling your armor skill anyway, and it'll be mostly useless IMO.

Ok, that's a good point, I didn't level my alteration mage past level 20 so maybe at the endgame alteration is more viable.