There is already skills that cost 3 memory slots in the EA (found a necromancer skill like that). I think this balances the game if OP spells cost 5 memory slots, it's a choice to make, will you take it or have more spells ?
Anyway, you're right, it feels odd and it forces you to put points in some primary stats.
I feel like there should be something else. Someone played Path of Exile ? In this game, you can level up your spells after using/xping them and leveling them ask you better stats to still use them and greater mana cost.
There could be something similar maybe ? You can level up spells after some XP or uses and the higher the level, the more it relies on high stats. For example a level 1 fireball would be for 12 intell (so more intell more damage) but a level 3 fireball would do greater damage but rely on a 20 intell (so you would lose the more damage from before BUT the spell does more damage itself or it can even be a greater zone or greater chance of CC or something else)
Well, going to make a topic about it !
