Honestly so much about how D&D does magic just doesn't work for me. It never has. Vancian casting is, and has always been, awful to me. Now they've added this concentration limit thing on top of that, for officially the worst magic since basic D&D. Ugh.
The edition that did magic the way *I* would personally like it was 4th (I know, boo hiss). It was very well balanced with all the other classes; it had built-in limits to how much it could alter reality to prevent casters from breaking the game (with more powerful effects available through ritual casting); it could be used often and with less reliance on resting all the time (30-minute workday instead of 5-minute workday, at least); it gave casters (multiple) legitimately useful things to do with their magic every round, no matter how long fights went on (no more being a bad dart-thrower instead of a wizard); it was less complicated and let new players jump right in and just play a spellcaster and be effective without having to comb through 100 pages of spells first, trying to figure out what they all did and then remember all of that besides. People like having attack cantrips that they can cast all the time in 5e? Yeah, 4e gave us that. They were called at-wills, and they made casters 9999 times more fun to play (especially at low levels, which let's face it is the vast majority of where most D&D groups play at any given time).
Honestly I am not a fan of casting in any of the D&D editions, but spellcasting the way I would do spellcasting is way too finicky for a tabletop game, where it would involve tracking lots of minor changes in order to maintain its immersion. Video games don't have this restriction, they can do all of that busywork, but unfortunately if you are making a D&D game you can't exactly go and completely rewrite spellcasters from the ground up to fix them, you need to stick to the rules. On the other hand, sadly it seems that in most cases, when a developer is not tied down to the D&D system, they opt for a more simple ruleset without as much depth as D&D, when this should not be the case.
Mana systems are something video games hold over tabletop, which are criminally misused. You can make very interesting mana systems for spellcasters which would heavily impact gameplay, for example, a modified version of the spirit eater curse in NWN 2 MotB, where the more mana you use, the more addicted you become to it and the more downsides there are. Or you could have a world where the main currency is the casting resource and so using magic always burns your money, which adds an interesting element to resource management where you must consider buying items or burning money.
As for video games, you know which one had an awesome magic system? Tyranny. Check out the magic in that game, it's so cool. You could design your own spells, you didn't have to rest to get magic back, it was just fun.
I absolutely agree here, Tyranny's system was great and had a lot of potential.
