What would you change in Heroes of Might and Magic IV?

I only played TGS 1.00, so I might not know much.

Well, the game was being refined:

fireball and fire ring

It depends on what you consider similar... After all, the first one simply hits an area, while the second one has some caveats. In the 3rd game, they are also present, only the ring is icy.

explosion or split

The difference is actually very big. After the split, the unit cannot be resurrected.

confusion or hornet's nest (although I might be wrong), haste and quickness

These are very similar, and the first strike and serpent's curse are also absolutely identical spells. However, in 3.6, they want to give the serpent's curse the opposite effect.

it cannot be considered balanced in any case

Why? The spells do not compete with each other; they all have different aspects of application, and there are only a few that are somewhat similar at level 5 (mass cancel, divan, sled).

But the fact that there is no red orb is a pity:( It would be more interesting...