Theres also various fire resistances, but i agree that spell turning shouldn't work...

If you want somewhat of an ULTIMATE spell caster for soloing i'd suggest downloading the druidic sorcerer kit - the mystic thuerge kit uses the wizard spell book in the same way as a sorcerer but can also cast druid spells in it - and its HLA's are just ridiculous, the high level quintessence magic causes the gods themselves to fear you!

...So obviously the kit becomes somewhat Overpowered pretty quickly and may be a bit too easy to solo with

There's no need for that. Just plain Sorcerer will demolish anything into oblivion.

Aye, i tottaly agree with that, even with pretty dodgy spell picks the game isnt impossible to solo with too much difficulty.
However, since this thread seems to be after some ultimate magic slinger / power gamer character I thought i might just add my 2 cents

I'm sure Spell Turning only reflects single target spells, perhaps you think of Spell Deflection?

Another question on my "solo" journey is; what did y'all do as far as individual char. quests?

Spell deflection doesn't touch area of effct spells either. (minor) globe of invulnerability and spell imunity will be the only things that'll do that

If you mean the NPC quests, such as Keldorn's quest with his wife and such, i personally just dont do them. There are some however that you dont need the character to do, Nalia's Keep for one, the planar sphere is another. Both of those quests are good for solo mages to do. Some nice items at the end of the sphere quest for mages, and plenty of loot to sell from nalia's keep.

Other people will pick up the NPC in order to do the quest, and leave them as soon as possible (or leave them sitting back while your PC does the work) you only get 1/2 exp that way, but solo-ing the game, you don't really need exp that much, there are more than enough ways without NPC quests to max out your exp in the game.

There would be only two reasons to take NPC's along with you if you're soloing a character
1) You're an XP hogger. You don't want to miss out on any XP. This involves taking Imoen along with you through Irenicus' dungeon to clear the traps.
2) You're a fervent roleplayer. Your character would not sit by idly when a paladin needs you help. This argument is weaker IMHO, because the quests of the NPC's come up once you've enjoyed their company for at least a little while.

Both rely heavily on reload knowledge, a thing I'd like to avoid as much as possible.

Well, that might be valid if most solo characters didn't hit the XP cap by chapter three.