For some reason my heal prediction as a paladin dos not work properly, downranked spell are shown without addheal whereas max rank spells are exaggerated.

I agree with this issue. I downranked my Renew (Priest) and it stopped showing the incoming heal bar with a Heal prediction timeframe of 100. I did not have the issue of exaggerated healing though.

Concerning the HoT issue, since I want the full value, I could just reverse commit pull request #508 to get everything working

EDIT: Nevermind. It doesn't fix it entirely. Sometimes, the HoT does not appear

See #585 (comment)