I think it’s an interesting question to ponder how exactly an elf (of any race) learned and uses magic.
Firstly though, I think that generally a mage can only really do one thing at any given time. An elven mage mage have learned how to cast frost, fire, and arcane bolts, but they’re probably not firing 10 different kinds of bolts, one kind per finger, all at once. I don’t imagine an elf brain’s ability to concentrate on multiple things at once is any better than a human mage’s. The elf might also know a super duper whatsits spell to do things, but war isn’t exactly conducive to making optimal casting conditions - the opponent needs to die and they need to die now. They may know a thousand different ways to cast a magic bolt, but there’s really only 'nuff processing power to do one at a time at a particular speed.
One thing I really liked about the warcraft movie was the scene where Medivh made that lightning wall thing. He was in a super optimal place - high ground so far above both allies and foes that he was practically unreachable. And it took a lot of time (relatively speaking, combat time) to do it. These things can definitely be factors in limiting elven mages.
Another interesting example is education - IRL, people are learning calculus earlier and earlier. Heck, I’m not too far out of HS/college, and I’m already a little bamboozled at how much earlier kids are learning the things I learned these days. People can very easily get set in their ways as they age, and while an elven mage would live hundreds of years making advancements in learning, concentration, and fine tuning power manipulation techniques, a human born 1001 years after an elven mage could have access to all the fruits of those labors. They wouldn’t really have to learn everything from the ground up over the course of hundreds of years like the mage did - they could just jump right into the current state of things.
There are also niche limitations, like the Nightborne. I figure your studies can only get so far when you’re trapped in a single city with the same people for thousands of years. Sparring is all well and good, but it’s not like opportunities to practice large scale spells that’d be beneficial in war were common, and there’s no substitute for actual experience.
That all said, Blizzard isn’t exactly…Good in keeping capabilities consistent across characters, factions and so on. Their world consistency is shaky at best - surely the method for casting a fireball has advanced somehow over the past 10k years, but that’s not the easiest thing in the world to write about when an elf mage and human mage are interacting.
Oh! And it’s pretty established that p much all magic is addicting, somehow (except maybe Light? idk). It isn’t really something you see addressed often, but there was that one dungeon in DF with the arcane crystal-infected dragon who was clearly in a great deal of pain. Elves are probably very strict about their arcane usage over extended periods of time so they don’t end up the same way, and even then they still ended up…Y’know. Blood Elf and Nightborne issues. Fel, arc wine, etcetc.
I do think that’s something interesting to explore, especially with arcane magic, which is kinda treated like the equations-math-superconcentration-college degree of magic, compared to something like Fel. For arcane, the users are likely more reserved - they’re not casting 24/7/365 for thousands of years on end. Not that they won’t be better and stronger than a human mage, imo, but it’s a limiting factor…
That isn’t exactly present with Fel. The difference between, say, a Man’ari Eredar and a human warlock versus the difference between a 10k yr old Night Elf mage and a human mage would, imo, be quite different in a lot of ways.
The Man’ari is probably orders of orders of magnitude stronger than the human Fel user, just because they don’t really need to care about Fel corruption. Heck, they’re so corrupted they became demons and can’t be truly killed outside their home turf. They were probably encouraged - and heavily supported by the Legion’s resources - to go balls to the wall casting as much as possible AND were provided opportunities to do so in war time what with the whole…Y’know. Legion vs everyone thing.
On the flip side, arcane mages, even the old ones, don’t have that same kind of support or opportunities.
Now. I think a lot of this boils down to ‘Blizzard is just bad at writing this stuff’. But it’s also something I enjoy overthinking as someone who plays magic users at a lot of different strength levels. There should absolutely be huge differences between elf and human casters, but we know who Blizz’s beloved OCs are most of the time and it ain’t elves, lol.
Edit: Forgot something! Physical magic, such as Chi and stuff. Also a very fun area to explore and imo provides important insights into how other types of magic would also be limited.
Physical stuff. Elves are still fleshy. A 400 year old monk is still fleshy - I don’t imagine the measurement of their punching impact was completely linear across all several hundred years of their training, just because the physical body doesn’t necessarily keep up 1:1 with increased knowledge. If a 400 year old monk wanted to punch someone as hard as they possibly could, they’d have to spend huge amounts of additional effort just preventing their body from turning into a liquid on impact, if their frame could even withstand generating that much force. Similarly, a 10k year old mage’d probably have to spend tons of effort preventing the strongest spell they could possibly muster from blipping them out of existence. And, as I mentioned above, that’s probably a huge drawback on the battlefield…And I’d love to see Blizzard writing about the methods very old elves have come up with in order to diminish that drawback - such as apprentices or support-mages who can share the strain and allow for speed casting of even stronger spells. Buuuuuut I’m not holding my breath for that level of detail, unfortunately <_<