In my opinion, Ragnarok should be +10 strength, not just on Attack. It's the weakest item in the game, and it's useless unless you for some reason are attacking a city with one hero.
Basically, it's an item for Barbarians and then only on offense. At least as a personal weapon, it should provide its wielder with strength at all times. Imagine a lone hero standing in a city over a body of corpses, saying "I'll take all challengers!"