Not meant to be a visual indication of the aoe, more so a gentle persuasion of what is occurring.
Also meant to last for 10 seconds, if it didn't start damaging ASAP I would personally be a bit peeved.
@Devalut I already did. There's this singularity, then there's an expansion, then seething DPS flames. If you want you can put the big crunch in there and when the big flame reverses, there's another effect on those poor suckers inside its bubble.