Among the various bits of mechanical info that’s been revealed about Warlords is the fact DoTs and HoTs will no longer have “haste breakpoints” and will no longer “snapshot” your stats at cast time. Celestalon has mentioned this a few times on twitter and frequently responded to questions about it. Since a lot of people seem to have questions on how the math of this breakpoint-less system will work, I want to to explain some of the behavior that will result from this. First, a brief history of this whole problem.
Current System: Haste Breakpoints and Rounding
Before Cataclysm, haste generally did not affect the rate of DoT ticks. There were a few exceptions, such as the Glyph of Rapid Rejuvenation that caused the tick rate of Rejuvenation to be affected by haste. But this did so by shortening the total duration of the HoT and keeping the number of ticks constant, so it didn’t have to address the big question of DoTs and haste: what do to with the fractional ticks that appear when you do this?
When Cataclysm introduced a general mechanic whereby DoT ticks would be accelerated by haste, it handled this problem by changing the duration of the DoT, rounding it to the nearest integer number of ticks.
To work an example: say a DoT has a 12-second duration and a tick period of 3 seconds. Unhasted, when you cast the DoT, a 12-second debuff appears on the target, and the 4th tick will occur exactly as the debuff expires. If you add 25% haste, the tick period will decrease to 2.4 seconds (3/1.25). Since 5 ticks at 2.4 seconds is exactly 12, you will still get a 12-second debuff when you cast the DoT, and now it will be the 5th tick that occurs as the debuff expires. But what if you only had 20% haste? Now the tick period is 2.5 seconds (3/1.2). Since there is no system in place for handling partial ticks, the game can either give you:
- A 4-tick DoT that lasts 10 seconds, or
- A 5-tick DoT that lasts 12.5 seconds.
In fact, you get the latter. The game rounds to the closest whole number of ticks, and since in this example, the 5-tick option is closer to the default duration of 12, that’s what you get.
Finally, if you had 12.5% haste, the tick rate would be 2.667. So a 4-tick DoT would be 10.67 seconds, and a 5-tick DoT would be 13.33 seconds. These are equidistant from 12, and this is the oft-discussed “breakpoint.” At any higher amount of haste, you get 5 ticks, and at any lower amount, you get 4.