Woah, let me stop you right there.
The spells in Skyrim are AWFUL and TOTALLY worthless. You end up casting about 3 different spells: Lightning Bolt/Frost Spike/Fire Ball, Summon Fire/Frost/Shock Atronach (sometimes I switch back to fire because the frost atronach is too big to fit through many doorways and thin cave passages), and fast/quick heal.
Its terribly unforunate that other spells like the wards and shields are so worthless. They don't protect enough (100 armor compared to the hundreds that warriors get?) or they're too cumbersome to use (The ward spells are AWFUL because of this. When you most need them is when you can't use them. If you take the time to switch to the ward spell and bring it up to block, you're most likely already dead, or the ward breaks and you get staggered).
The removal of spellmaking effectively neutered magic as an effective system, at least without scaling. The mage starts out trying as many different spells as possible, feeling about for usefulness, and quickly discovers that they're going to be using basically 3 or 4 spells and that's about it. It doesn't help that using spells is so cumbersome, as you have to equip them like any other weapon. As others have mentioned, this ruins characters that use two handed weapons along with spells, because you're constantly switching back and forth and it gets far too cumbersome to keep playing. Even as a mage its cumbersome, because attempting to use two spells at once is suicide, because you lose the stagger from not dual casting destruction spells.
I think magic may be too far gone to even fix by adding scaling to destruction. Its just a fundamentally flawed system because its lost so many spell effects and so many others just don't work out for the player.
Believe me, I understand there are issues with the damage and cost numbers, but I'm talking about the mechanics themselves. There's no spell in Skyrim that succeeds in being more utterly worthless than, say, burden in Oblivion. Because burden was always a worthless mechanic - NPCs never carried enough gear that it'd ever be worth a damn against anyone but the PC. The spells in Skyrim that are worthless are only worthless because they don't do enough damage and/or cost too much magicka, not because the concept of the spell is bad. Although I have to admit, the magicka damage aspect of shock seems to run into similar issues since NPC mana seems to be too high for it to make a difference. I can't say for sure though since I never bothered really going into the tree and specializing in either.
Wow (again)..... really really really???
Seriously though... spell making did not allow you to deal with every encounter in an imbalanced way it just gave you more flexibility - which is great. Mana costs / attributes of spell you created were well balanced too.
You can't possibly want to spam 1-3 spells in each encounter and really believe it's more balanced because you lack the flexibility to do anything else.
Limiting the gameplay choices to get challenge? Do i have to explain why this is ridiculous?
I can't believe you truly want this.
Really really really. I use these spells -
Muffle
Calm
Frenzy
Conjure Dremora Lord
Bound Bow
Fast Healing
Soul Trap
I'll use the courage based ones once I get Master of the Mind so I can buff my dremora too, and invisibility when I get 75 illusion.
In Oblivion I used this -
Fire Damage 5 pts on touch
Drain Health 50 pts on touch
Weakness to Fire 100% 2 seconds touch
Weakness to Magicka 100% 2 seconds touch
Invisibility 2 seconds on self
With a plain invisibility spell just to close gaps unnoticed. I may've added fortify speed to that at higher levels just faster travel. Could add various other things to the above spell at higher levels too, but that's the basic idea. Nothing would react to me killing it, my mana regen was fast enough since I stacked wisdom that I could cast it infinitely.
2 spells, only really needed one, every enemy was trivially easy to kill. Didn't have to exploit chameleon or reflect, could even make a minor version of the spell at lower levels but wasn't necessary with low levels being so easy. Basically, once I hit level 10ish, I could kill everything not only without getting hit, but without being seen.