Remove smithing, enchanting and alchemy for a bit. Know what? That doesn't improve Mages at all. Do you know why? Because the physical classes still have a much easier time thanks to weapon upgrades and skill increases. They won't be rushing to Daedric+++ items to blindly plow through the game, but they will still be steadily increasing from 1-50 or whatever. The way level scaling works in this game and because of how some elites seem to have ten times the health of trash enemies, it makes it much worse on someone who relies on a blue bar to deal all of their damage. The other problem is that the spells actually get more inefficient as you pickup the new versions. Sure, the cost drops as your destruction skill raises, but they are still less damage for the cost compared to previous spells. Then you have people saying "well lol all you need to do is powerlevel enchanting so that your spells cost nothing". So I should be forced to raise a crafting profession to it's max to make my damage tree viable? No physical class has to do this, and doing so with them just trivializes the game. You don't even need Enchanting/Alchemy on Adept level for physical classes to make it way too easy. Even on Expert, Smithing skill lvl 100 gear is way more than enough to easily plow through the game.
I agree that scaling is an issue but as I said, the tweaking has already begun. The mod I mentioned adds +10% damage to the Expert and +15% damage to the Master perk. The goal is to make the damage based on the level of Destruction but without the Creation Kit it seems to be not doable right now.
I still think that Expert and Master difficulty should not be a cakewalk. However it is a cakewalk for physical classes but that doesn't mean mages are screwed, it means physical classes are overpowered. You should never oneshot a level scaled enemy on Master.
By the way I haven't powerleveled Enchanting so I don't have -100% cost. I use the gear I found which gives me around -50% cost and 100% (or more, can't check it right now) faster regen and I got the faster regen perks from Restoration. I still run out of Magicka sometimes but I use the health-to-magicka spell to refill my blue bar then a healing spell to refill my red bar. Works like a charm.
You say that it's wrong to be forced to max out Enchanting to be a viable caster but you agree that maxing out Smithing makes a physical class' life much easier. Isn't the two pretty much the same?