You're not getting my point here - I can cast any of those spells for 1-2 mana due to cost reduction. Affinity + Path of the Mage + any caster item and any concept of mana balance goes right out the window.
That's ignoring the irrelevance of tactical mana costs once you're past a certain mana threshold anyway, as there is no limit on the amount you can spend in one battle.
Again, what's wrong with adjusting the traits and items and also spell costs so you dont get 1-2 mana for the powerful spells? Or simply saying traits and items have reduced bonuses for higher level spells etc.. Dozens of way to balance.. To throw away the mana system for some untested system that probably has even more flaws is odd...
And then on top of that, there's no great way to tune mana costs based on a variable mana income from shards and buildings, either they're cheap enough to use early game, or they're too expensive to use without a considerable mana income, leaving your ability to use magic to any significant degree up to the whims of the map generator.
I don't believe your thesis that there is "no great way to tune mana costs based on a variable mana income from shards and buildings", but say I do..
You play the hand you are dealt. Or should every game end with you being able to cast every spell with 1-2 mana? Some games due to the settings, the variability of the map will be high powered magic games.. some won't. In some games, some strategies will be better, some spells better.. I don't know why you think this is a problem.
Your cool down system is to artificially force players to cast all spells..even the poor ones.. It's a interesting concept that not many games in this genre have. But I rather have many interesting spells I have to ponder and decide to use then a artificial system that forces me to use inferior spells that I don't want to, simply because I already used the better ones...
Of course you will never succeed in getting all spells equally good for it's cost, but I rather try for that, then throw my hands up and give up and say.. i let you cast each spell once so you will be forced to use all of them.... That's so "binary"... Just throwing it out there..i rather have "soft" limits so maybe casting the same spell twice in TC , the spell costs x% more?