This isn't a complaint about mages; quite the contrary, I recognize this as a problem I caused by building the character wrong.
My point is, pure mage is one of the character concepts that can be "built to svck" if you do it wrong. Not the game's fault, it just requires a more careful build.
Built your character wrong.
For most classes in Skyrim, building your class wrong means Master-difficulty has been accidentally broken and the game is too easy.
My smith/enchanter/one-hander broke the game at level 27.
My conjurer/archer broke the game at level 10; Bound bow beats every other bow in the game by lightyears unless you pick up smithing and enchantment and make a better bow.
My destro-mage was brokenly useless at level 17, and reading on the forums, only exploits can improve her to the point of usefulness.
In D&D, she's a elemental, necromancy and alteration-caster.
(Death-spells, elemental damage and slow, haste, transmute effects -- not summoning).
I even perked into armor with her to keep her alive.
Destruction is not good without the -100% casting cost exploit.
I call it an exploit, because "free ulimited magicka" doesn't make much sense.
Considering some spells cost 1400 mana, 0 spell cost...
I just can't help imagining the items with the enchantments glowing red and melting after 4 seconds of supplying infinite mana to the caster at the rate of 1400 mana per second.