Anyone else feel Zekes can be hard to proc at times?

I have bought this item a couple of times on Leona cause the idea of her having an AOE Slow field just sounded like the ultimate dream, but most of the time I use it I get the base storm but then I never get the empowered storm very often. I know it gets proc'd off of you hitting a burning target but can anyone on your team put the burning affect on them or does it have to b e the one you bind to. I prob just misreading the tool tip but it just feels like it never procs for me even if I hitting the same person everyone else is when I got the storm going