I've seen
Balanced Magic recommended, but I haven't personally tried it, so I won't vouch for it. Still, looks like it has some impressive tweaks that will make things slightly more favorable for a pure mage vs. leveled opponents. It does change the perk trees around for the magic schools, so you might not be able to use it on an existing save.
this is all very sad to hear, and I'm discovering it now with my level 28 mage. I'm at, I think, ~58ish destruction with the adept level spells (chain lightning and such), and each "upgrade" (the spell tiers are
drastically far apart) I've noticed only a very minimal gain in damage, yet a substantial decrease in magic pool.
I went right from my apprentice level robe (12/75)--the other upgrades are too freaking expensive--to archmage robes and Morokei mask. So, I go from 75% magic restoration to 200%, and have had a 20/20 ring and necklace for destructo cost reduction.
....I have noticed nothing. I still get as many casts before my pool drains, and I still have to wait. I'm at 300 majicka with +50 on the archmage robes.
the other spell trees don't really offer much in terms of useful offensive spells, or something that actually affects your foes in any real way. it's all either damage protection for yourself or summoning meat shields.
I've unlocked several of the Midas Magic spells, but those don't offer all that much, either. Magma ball is pretty good, but most of the spells are prohibitively expensive to cast.
I suppose I should try this mod, but I might need to use console to remove some perks in alteration that I spent (trying to unlock magic resistance), as that looks to be the tree that is altered.