Its been my experience that an inexpensive hindrance like a wall of fog can be a real life saver under very specific circumstances (hence it being a level 1 spell, so even if it's out of school it's only 2 spellbook points).

Quick casting that fog bank during the initial quick cast phase might save a creature (or even your mage!) from being shot by said skeleton archer, even if your opponent has the initiative.

Edit: As for the wall of fire being able to be shot down by arrows, I suspect that it's a major balance issue to have a wall such as that have such strong immunities. Then the wall would have to cost more to justify its difficulty to kill, meaning more mana for less utility.

Blew through the apprentice deck's eh?  

Have you gotten the itch to build your own deck yet? Make sure if you're going to stick with pre-mades to look up the revised versions of the spellbooks as from what I understand they're much better (and you can have all four decks constructed at the same time).