it also doesn't seem to have much of an impact on damage that you take, at least for attackers in your health range
Oh I mean: does the OPPOSERS defense affect the punch damage? So does this mean that no one can be safe from punches, our defence doesn't help us? :O
Yes no one can be safe from punches, your defense doesn't help you from what I've seen, it's based on health. Max damage dealt in a battle is also done through health stat not attack, attack helps you win the battle and reach that max damage though.
Okay, let's suppose that you are in a battle with another Viking, let's call that Viking B the "ceiling" of damage is determined by the lowest of your two healths. For the sake of an example let's say that Viking A has 1 defense and no battle strength but has 50,000 health and Viking B has 5,000 attack, 50,000 health, and 1 million battle strength. Player B attacks player A and the damage player B can do to player A is capped at a certain number (probably 13,000 or so for 50k health). So without any defense you take 13,000 damage. Defense (both the personal attack number and your battle strength defense number) will help "soak up" some of that damage and lessen it. So if you have 6,000 defense and 1 million battle strength and you get into that battle you might deal 7600 damage and only take 7400 damage, you would win that battle. Basically, it does not determine the "ceiling" of your damage, health does but it determines how likely you are to make the damage in a particular battle roll in your favor. tldr; add health if you want more XP, boss damage, raid damage, and to deal more damage to players- add defense to win battles more often.