User blog comment:Masterzach32/Clovis, the Assassin of Demacia/@comment-24574897-20140310184415/@comment-4434378-20140310202936

The passive is actually not per second. So basically it would only be really high damage if you had gotten all 4 stacks on a target, at which point it is 4% max health per second, and it required 4 autos to apply.

Brand: 2% every second as soon as he lands a spell

Clovis: 1% every second as she lands an auto, stacks 4 times