All normal hits used against an enemy have a chance of being evaded or blocked. This is calculated by weighing the attacker's hit chance stat against the target's evade or block stats. Powers cannot be evaded, but they can still be blocked.
To determine the probability of an attack landing, the following formula is used:
Chance of evasion = Target evasion stat / Attacker hit chance stat
So for example, it the attacker has a hit chance of 144 and the defender: evasion 35, that gives:
35 / 144 = 0.24 or 24% chance of evasion
Naturally this means the attacker has a 76% chance to hit
The creatures in the game have a very high evasion rate, so it's better to test hit chance on other players instead
Will be updated soon, the evasion, block and miss system was updated during the 1.6.3 update and this information is no longer correct.