I recently got a ToV healer mace with a proc, and decided to have some fun meleeing through an LDoN with it while my Monk tanked things etc. This also led to the discovery of a bug with Yaulp.
Currently, Yaulp does not stack with, and overwrites, Hastening of Salik, which is the Buff Bot haste. The problem with that, is HoS pops me up to 100% Haste, while Yaulp overwrites and drops me down to 36%.
Tested this on the bot, Yaulp'd and then tried to buff, HoS won't overwrite it, and Yaulp overwrites HoS.