Im not looking for more of a challenge or anything ive played through on skyrim on many different breeds of characters and builds, alls im saying is in my experience being a full mage is quite easy even on master, all i did basicly was suffer a bit till i got arch-mage gear and played untill i got my enchanted daedric armor now i don't even need any followers i just run around with infinite mana casting thunderbolt on anything and every hit stuns and beast, dragons, alduin, and specific quest dragon, literally anything every hit stuns along with chain lightning if you find yourself in a pickle or unrelenting force, i zipped through the quest in about a hour n a half with no potions needed, and i travel aimless through skyrim with out fear.
The only other that comes close i think is a thief but they don't kill as swift to my liking.
as far as overpowered characters go mage is at the bottom of the list. you killed everything super fast and thought you reached the top of the mountain but you didnt. Without using any cheats, just normal in game abilities(necromage + vampire, all the crafting skills stacked) you can get.
orc with maces who does 940 damage with one mace, dual weild, orc berserk, one handed buff enchantments puts the damage at around 8k damage with one swing at 75% ignore armour. you took the end dragon(forget name) down in 6 hits, I did it in one swing with spare damage.
He had 80-85% magic resist AND magic absorb AND physical resistence
900 life because he had free casting on all schools of magic and unlimited powerattacks/stamina
Had silent running, +80% sneaking
After the melee characters the next strongest ranged character would be with a bow not with magic. Magic is limited in damage by the spells at like 150? per hand. A bow can do 900 damage before sneaking bonuses. A bow can one shot the end dragon with proper sneaking damage mulitipliers.
None of the characters would be less protected than the mage. Last thing Ill say is the half casting cost perks are useless. You dont need half casting when you have 100% reduction to schools