It's an instant handicap taking a mana mid, a la Ryze, against non-mana mid, a la Zed. You're not only constantly micromanaging your mana output, but you will likely have to back to fountain before he does. Just absolutely ridiculous. There is nothing in the game that makes mana regen at least on par with energy champs.
And don't even get me started on yasuo mid, who not only does not have mana or energy, but a double passive to shove down our throats.