Posts from Poll: Preferences when choosing skills in Heroes of Might and Magic IV.

Actually, I believe that the hero is more important than the army; you should only build an army in the campaign, but in multiplayer, the hero is more important.

My experience with online play (although modest) also suggests that you need a sizable army. But the hero, I agree, plays a bigger role than in a game against the AI.

Regarding the computer opponent, I think one commander and a few basic units will be enough. The computer is not very smart and is easy to defeat.

First, scouting, then stealth!

Personally, I believe that an optimally developed hero looks approximately like this:
Tactics
Warfare
Magic of Life
Magic of Chaos
Magic of Order

If you're building a Mage, you absolutely must level up their Warfare skill! It's a golden rule!

For me, it's not essential. I've only recently started paying attention to it, but I almost never put it into practice. My mage survives anyway. Although, I won't hide the fact that sometimes I protect him like the apple of my eye. But what can I do if it's more important for me to level up extra magic than Resistance and Combat?

for me, it's more important to upgrade extra magic skills than Resistance and Combat.