1) Armor or Alteration? If you only had the perks for one skill, is alteration or an armor skill best for a mage?

2) How much damage can I expect to be dealing? If I use expert level spells, they are concentration, right? Therefore I would not have impact? How about dual casting adept with fully perled int hat element (ie: augmented flames)?

1) Depends. With alteration, you have to spend magicka that you might want to use in battle, and the spell only lasts a certain time, but armor doesn't suit everyone. So I'd say it depends what kind of person your mage is.

If you HAD to choose, go armor. Personally, I'd go for both. That's what I have on my character, anyway. Also, go for light armor. The perks in that are better, IMO.

When I played my pure mage (no physical weapons, no physical armor) I started out using Alteration a lot for shield spells, because I thought that's what a mage did. After awhile I didn't see the point and stopped using shield spells altogether. I had a good Conjuration/Destruction routine going and rarely got hit. I played that character to about level 45-50, and after about level 10 my character played the rest of the game with 0 armor rating. And, paradoxically, that character probably died less often than most of my armor-wearing characters.

I have to agree with this.

If you know what you are doing as a mage you really shouldn't need to much defense.
Illusion or conjuration make for great crowd control skills.
Thats the first thing a mage should go for.

After that go with either a deffensive or offensive skill.
Destruction,Alteration,or Resturation.

Then you can start to branch out.