thats why these separated magic schools is bad
better would be defensive or offensive mage

Well, aside from the fact that lightning works best on sea creatures and robots, and fire works great against trolls and many types of undead, and so on.

(Of course, whether this is enough to make the element choice interesting is another matter.)

Why should XP have to be spent on the specific school?

(Random SaGa fact: In some SaGa games, the main healing spell is Water, but Fire includes a spell that will auto-revive a character (at full HP) if that character dies, and sometimes a health regen spell.)

(Randome SaGa fact 2: The powerful healing ability Rain of Life has never been a water spell; in the two games where it exists, in one it's a monster ability (which is fortunately available to the player), and in the other one it's a Bewitchery spell (which was called Mind in another game in the series).)

Oops, I meant skill points :)

Hm? Pretty sure cold sorcs where the exception. At least in LoD, fire was the standard mf-sorc and lighting for brutal damage. Guess maybe some blizzard sorcs in the Baal run (especially when people use infinity inflationary and get some resistance reduction for any element).

Also played some private servers not long ago, which are in pretty decent shape (both, near vanilla set ups and full conversion mods like MedianXL). The normal battle.net is just terrible, except for the 5 days after the ladder reset when all the bots are not ready yet.

As I have stated numerous times in other topics, I think skill points that are gained solely through level ups is a design mistake.

nah they are fine , you level up you spend your points , better than stop gameplay with spending your earned point

It's better to just have your skills improve based off your actions, or at least have them improve in a way that doesn't make it impractical for high level characters to learn new tricks.

This becomes more of an issue the longer the game is.

(The problem is that skill point systems tend to lock the player into one particular set-up for the entire game, and that just isn't fun when you can't easily experiment with other builds.)

yep
but if you give a champ everything then it will be overpowered + makes different playthrous pointless
just look at Diablo 2 , you have different classes then different builds , game gives plenty of playtime due to this
diablo 3 removed a lot from this , then removing classes would just make the game bare bone one playthrou and that's all

Different.

I like the idea that maybe certain spells are stronger offensively, but that specialty may not be as good either defensively or say outside of combat.

Let's say that perhaps fire magic has a lot of offensive type spells, but maybe earth has spells like Level or Raise Terrain which can create new routes through a map or block off enemy reinforcements.

There are games where "element is just the color of the damage" or "flavor only" makes sense and work, too. Grim Dawn is one. But these games work and focus in different ways than others where asymmetry is the better choice. And they're narrower/harder to get right.

Another good example of asymmetry being the better choice would be Arcanum.

The magic college of Displacement provides teleport spells, and let's be real, Teleport is an essential spell. That college is not great at combat, but from a utility and world building perspective it has its niche.

From the tech side of things, Gunsmithy is great too, but of course from a combat perspective. Who would not want to slap together a Tesla Cannon from spare parts?