I have been debating making either an altmer or dunmer battlemage. The altmers have no weakness to magicka, and have more magicka than every1 and restore magicka faster. Dunmer have a racial ability that immunes them to fire then sets themselves on fire, how useful is this?

Neither power scales, so it's hard to say. But I imagine the Dunmer one will be fair for groups that surround you.

last i checked altmer have a 50% weakness to magic.

imho go with the dunmer for a battle mage. they are well suited for combat and magic.

As long as you can keep the enemy you're fighting in constant melee range than the Dunmer ability will do a fair amount of damage over the 60 seconds of its duration.

For a pure Mage role though, I'd rather have the Altmer's racial abilities.

EDIT: Altmer no longer have their weakness to magic. Why is this still causing people difficulty?

Check again. Theres no penalty anymore.