With patch 4.0.1 the way DoTs work has changed. In addition to all DoTs now benefiting from haste innately, haste now reduces the time between ticks. Haste only reduces the DoTs duration until an extra tick is received.
While affliction does not gain any significant amount of DPS by reaching any sort of haste "threshold" these values and how to calculate them are still good to know.
This applies to all of our DoTs except BoD, however, the haste required to achieve this extra tick will differ between DoTs. To calculate the required haste to achieve an additional tick we would need to calculate the time between ticks, specific to 3 decimal places.