So Nerds, lets talk about Rejuvenation math!
When calculating your rejuvenation (or any HoT in vanilla) you use your +heal * duration/15. So since Rejuvenation is 12 seconds it is +heal*12/15 or more simply +heal*.8
The second penalty applies to spells learned under level 20. For rejuvenation this is ranks 1, 2 and 3. This penalty is
(20 – [Spell Level]) * 0.0375
Now here are the interesting things! If you have the Idol of Rejuvenation it adds +50 healing to Rejuvenation. So originally I just added this to my +heal and was wondering why the numbers all seemed ever so slightly off. But the HoT penalty (in our case 0.8) isn’t applied to the idol! Unfortunately the under 20 penalty is 🙂
Here is another thing. If you have full T2, then your rejuvenation gets an extra tick, and now lasts 15 seconds. So you might think that +heal*15/15 means no penalty right? Sadly, that is wrong 🙁 It counts as an extra tick, not an added duration. So it still calculates as if it was 12 second duration.
Anyway, check it out in action on my rank down calculator 🙂