Yup I got it that way too. I found it only works when you don't push in any direction on the analog stick instead just mash Circle when a enemy is very near the edge of a roof
Used the Lightning Storm for the first time last night (since the demo) and boy does it feel soooooo good. Was weird though as I got the last 2 stunts at once and didn't even realise till I saw the all stunts trophy come up (I was on top of the substation opposite the Gas Station obliterating everything in sight with unlimited power).
Most fun mission so far