It drops off a lot, i just wanted to support my issue with numbers i am using skada since you asked for debuff uptime last time i mentioned this problem, that the bot keep spamming incinerate when it should keep immolate debuff up or cast chaos bolt on high embers. I can actually see the bot trying to cast immolate or chaos bolt at the right time (yellow border appears on the skills on action bar) but it does that right in the middle of an incinerate cast, sometimes it just gets lucky to get cast an immolate or chaos bolts off. It seems like there are 2 bots are doing the rotation, first one just keep spamming incinerate and the second one tries to get other spells casted.
So to sum things up, what happened in that log that my immolate debuff uptime was low 55%-68% but at the end it went mad and kept casting immolate every 2-4 seconds. Sorry about my english not my first language.