Attenuation

Attenuation is a soft cap on experience earned during combat.

As experience gained from combat approaches 15 million experience points per hour, you will gain a debuff that slows down your gained experience (this debuff will be visible on screen next to the pooled experience displayed in the skills UI). Note that this ONLY applies to experience received through combat in Online mode. (For example, experience gained from quest completion is not limited.) Offline mode has no soft cap on experience.

Trivia

 * Attenuation was added in Release 49 in order to allow the addition of endless wave experiences, which are used in places like the control points.