well, first off I'd like to say, for the record, that I did in fact abandon my mage char in skyrim to take up a thief char (though to be honest it was largely due to her hideous forehead wrinkles (she was a breton), will probably try again once more appearance mods are released).
be that as it may, I didn't find magic to be that weak at all, can take out mobs fairly effectively, and my mage did rather better than my theif in a crisis. If a snowbear leaps out at my theif, she dies, whereas my mage can just blast off some fireballs. Alchemy I found to be one of the best skills for a mage, if all you do is alchemy and destruction, you have a viable char (though difficult), can be time consuming, and it requires you to stock up on a lot of potions before a fight (various enhancements and mana restoration ones, I've made a few that resist fire damage and restore mana, are handy when fighting dragons), at high levels alchemy can offer you that same sort of invincibility a warrior in fully upgraded daedric can have.
few problems I did face:
1. can be sort of a gap in levelling, due to the way the perks are set up, so that the mobs around you are getting extremely powerful, but you don't have the skill in destruction high enough to get the 50% less mana perk, which means all your high level perks are more or less useless, so you're left kiting enemies and using basic spells until your skill goes up.
2. happens a lot with #1, is running out of mana. Simple thing is, a warrior can keep swinging his sword, an archer can keep shooting arrows, but if a mage runs out of mana, they're completely screwed (never travel without a companion!), the risk of playing a pure mage, is that you really have no viable fallback weapon.
3. some spells seem rather difficult to use in a fight, ward spells for example, what good is a ward from one direction when i've got draugr trying to circle around me? more effective to charge up an extra fireball.
be that as it may, I didn't find magic to be that weak at all, can take out mobs fairly effectively, and my mage did rather better than my theif in a crisis. If a snowbear leaps out at my theif, she dies, whereas my mage can just blast off some fireballs. Alchemy I found to be one of the best skills for a mage, if all you do is alchemy and destruction, you have a viable char (though difficult), can be time consuming, and it requires you to stock up on a lot of potions before a fight (various enhancements and mana restoration ones, I've made a few that resist fire damage and restore mana, are handy when fighting dragons), at high levels alchemy can offer you that same sort of invincibility a warrior in fully upgraded daedric can have.
few problems I did face:
1. can be sort of a gap in levelling, due to the way the perks are set up, so that the mobs around you are getting extremely powerful, but you don't have the skill in destruction high enough to get the 50% less mana perk, which means all your high level perks are more or less useless, so you're left kiting enemies and using basic spells until your skill goes up.
2. happens a lot with #1, is running out of mana. Simple thing is, a warrior can keep swinging his sword, an archer can keep shooting arrows, but if a mage runs out of mana, they're completely screwed (never travel without a companion!), the risk of playing a pure mage, is that you really have no viable fallback weapon.
3. some spells seem rather difficult to use in a fight, ward spells for example, what good is a ward from one direction when i've got draugr trying to circle around me? more effective to charge up an extra fireball.
You won't notice a problem with mages till mid to late game when destruction scaling stops. However, I started to notice it was difficult in my mid teens and twenties compared to other class types I played. The damage of dest spells are just weak