#1 - Feb. 26, 2016, 11:20 p.m.
First 'Bug', the 'easy' one: Cultivation does not proc from the initial burst Rejuvenation heal. It only procs on Rejuv Ticks. I'm unsure if this is intended or not.
Second 'Bug': Cultivation heals every time it is refreshed. This looks... really, really weird in the event list, and has some really odd behaviors.
The first oddity is that it does not refresh consistently. It seems to only refresh the HoT when the refresh would add a full extra tick. This causes additional weirdness, such as cultivation doing *less* healing after Flourish, because for the entire extra 6 seconds it stops getting these extra ticks from the refresh, and two rejuvs (via germination) causing the same # of cultivation ticks as 1 rejuv.
The second oddity is that since the Cultivation HoT has the same tick-length as the Rejuvenation HoT, one Rejuvenation will almost always refresh it every tick. This is where that 'double tick' people have been seeing with it is coming from. Basically, Cultivation does a tick, Rejuv does a tick, then Rejuv refreshes Cultivation which causes a second 'tick'. This also contributes to the 'no extra value from Germination', because 1 rejuv will double the number of cultivation ticks all by itself.
A log of my fiddling with cultivation a little can be found here, for the interested.