What is your opinion about Heroes IV?

I agree, the Druid is the best hero, at least among those I've played...

Exactly. If the Druid is the best, does that mean the others are terrible?:) It should be possible to play with EVERY hero without any inconvenience.
For example, the Rogue is completely unsuitable for combat,
the Sorcerer only has one spell (by the way, Chaos magic should deal direct damage, not all sorts of cat reactions and bloodlust) of Chaos, and even then, not always when needed (for example, Sparks only work at melee range, which is useless!).