It's powerful, yes, but placing the player in a situation where they cannot progress because key items are damaged is hardly working-as-intended.
The problem is mana usage vs damage output. I don't recall the exact numbers, but even at maximum proficiency the lightning variants do more damage per mana spent.
Absolutely agree wit this :)

I reached the third dungeon and I can't do the first combat. I find the game hard if you don't know how you are supposed to play it. Second dungeon under the old mage building was hard already but with a bit of preparation - training and some stuff - I had managed to get out in one piece. So I assumed that grinding was unnecessary and jumped almost immediately to the Celtic continent after I got the fourth character (I didn't even know there was a magic trainer in the Iskai city).

The second thing is that the game is filled with "hurry" messages that I interpret as hidden timers, even at the very beginning of the game when Tom is hailed to pilot the shuttle, but I don't even know if these are indeed timers and if so, how do they count. This actively discourages the idea of grinding.

(my other problem is I don't have anymore a save from before I'm given the disappeared mage quest)

There is no need to hurry anywhere, you can take your time to explore, grind, ... (even at the very beginning of the game when Tom is hailed to pilot the shuttle, you can safely ignore it). The exception being some timed puzzles in dungeons (like press the second button within a certain time since pressing the first button).

You can grind outside the dungeon by fighting creatures in the wild (they respawn after certain time) or by fighting bandits in the mountain pass.

Yes I figured that the messages were just cosmetic, there are actually no timers. I just finished the Gratogel dungeon and boy was it tedious. Because I DIDN'T grind at all in the first zone, everything was super hard. My characters die in a few hits and never touch the enemies; the only really useful thing was Melthas' fireball.

I'm in Maini and the game becomes more and more frustrating. I still have the almost basic equipment for all my characters, I can find no money (I have 100 gp), monster loot brings very little money, I can't even buy the lvl 5 spells at the Iskai city, monsters kill me in 3 hits, spells cost a lot of mana and I have to wait forever to be authorized to sleep, Iskai spells cost those EXTRA seeds that are super hard to find, and even progressing in the story is hard.