As of patch 4.0.1, DoTs no longer can be 'clipped'. Previously, if a DoT was refreshed before it had expired, the tick timer was reset, causing a delay of up to double the normal time between ticks between the last tick that occurred and the first tick of the refreshed DoT. Now, the tick timer is constant. If a DoT is refreshed before it expires, the duration of the DoT will be set to the normal total duration plus the remaining time before the next tick. In other words, the ticks will continue to occur at the same time interval as they were, and the new DoT will have the normal total number of ticks, plus one, and have a duration between the normal total duration and the total duration plus one additional tick. This means that refreshing a DoT between the second to last tick and the last tick (the one that occurs as the debuff fades from the target) will result in zero lost damage or wasted globals.
Пруф
