This happened to me on normal a couple of times but on heroic it becomes a real problem. I would switch off to the energy sparks (i.e. the waves you have to kill) by tabbing / flame shocking them, just like I've been doing for years on my ele. At first I thought it was because I did it too fast, but a week later I waited a few seconds after they spawned and same deal. Even tried making a target macro and same deal. What basically happens is that flame shock is applied to elegon instead of the energy spark, as in there seems to be 1-2 seconds of lag, and it only happens to flame shock. Lightning bolt, earth shock, never seems to have that problem. I'm obviously hit capped and made sure that my flame shock is not missed. It becomes a real problem on hc when trying to get a 5th wave down.
Am I missing something obvious here and does anyone else experience the same?