Passive effects in The Secret World cannot trigger more than once per second. This means that some passive abilities or signets will not be as effective in combination with some specific abilities as a player might assume. If you want to focus your character on abilities that hit more often than once per second remember that some passives might not be as valuable to your character as they might appear.

Example:
The Assault Rifle ability Safety Off hits three times in one second. Passive abilities like Lethality build stacks whenever an attack hits, but Lethality will only build one stack each time Safety Off is used, since the second and third hits from Safety Off occurred within the aforementioned one second window.