Sorry Vertigo, I was just making a few broad suggestions. As Leto says, this is a very complex subject - depending on how complex your game is I suppose. When you look at how a game such as WoW works, the chance of a hit are based on dozens of factors - and even then I think it's still a bit too simple. You've got strength + skill with weapon + agility + class + other stuff vs the opponents armour + agility + dodge skill etc etc. It really is specific to your game and will require lots of testing to get it right.