King’s Bounty: Crossworlds

Yes, playing as a Wizard allows you to defeat everyone without losses, even if the enemy army is twice or three times larger than yours. Plus, there's a dragon, and although it's weaker than the Warrior's, it can still hatch 10 dragons from an egg and carry mana. These two abilities are what you should focus on developing for the Wizard.

Added 7 minutes later

The Rune Wizards were disappointing. They depend too much on runes :(. Without runes, they are weaker than some four-level units.

But starting with 18 magic runes, they turn enemies into sheep.

Added 1 minute later

and is it worth trying to play as a Wizard on the impossible difficulty level?

To beat the impossible difficulty as a Wizard, you need to steal maps.