[Kusasi]

493 is the point at which 2 of the 4 resilience effects are capped. Resilience does 4 things. Reduces critical strike damage, reduces the chance you'll receive a critical strike, reduces damage from dot spells and reduces mana drained from spells such as Drain Mana and Mana Burn.

Each of these 4 effects has a cap of 25%. However, critical strike damage reduction and mana drain reduction increase at twice the rate of the other 2 effects. So at 493 resilience, crit damage and mana drain will cap at 25% whilst the other 2 effects will only be at 12.5%. To cap these last 2 effects you would need almost 1000 resilience which of course is completely unrealistic. As redmage said, it's about balance. If you got yourself up to 600 resilience or something, you'd have to be sacrificing other important stats, resulting in you not being able to do any damage, and it only taking a little bit longer for you to be killed. :P