Pure Mage (I.E. no armor, or weapons) is just not a "No Brainer" style of play. You have to think, because with the heavy investment of Magicka, they have little Health, and without armor, they can be considered a little squishy. So don't Tank, the trade-off is, they're unencumbered, and with an Altmer being the tallest, they're also the fastest. The real advantage is versatility gained from the vast number of magical effects they have at their disposal.
Here's where the thinking comes in. You have to know what to use, and when. I just finished an entire article of
Battle Tactics | Skyrim Forums (scroll down to the second post) for the Wizard archetype. Not to shamelessly plug it, but I really don't feel like repeating them again, when I just wrote them all in 1 convenient place. A Warrior can rule the battlefield, but in the end, it boils down to get your armor up to survive just about anything, then attack until everything is dead, and finally, look for a new battlefield to do it all over again.
A Wizard can Control the battlefield. In fact, I highly recommend the Civil War for large enough battles to actually use it to the fullest. You can use Illusion to set everyone fighting each other, then AOE destruction spells to hit everyone at once. I don't really care for Alteration's protection spells, but I don't depend on armor too much anyway. They do an adequate job of keeping you alive, as long as you don't let them wear off, and stay out of the thick of the fray. It's much safer to be outside it, where you have a more strategic view, and can direct the tide of battle without worrying about the other half of it behind you.
Is it worth it? That really depends on the player. There's only one way to find out!