Which artifacts are best to equip a hero with?

Yes! And give them to a Barbarian! Or a Druid, and let him direct the dragon's power onto himself! But I'll trade this ring if I come across a "Warlord's Ring" or a "Protective Ring". After all, the army is more important!
Honestly, the game developers could have added a level restriction for wearing powerful items. They did something similar for spells!