the thing is that from my experience, people will easily kill you before the damage ramps up to a respectable number and the energy balls are so mind-numbingly slow that even a shielding reinhardt can sidestep them
Symmetra is a support character, if she's the center of attention she's basically forgeted. If you get someone while they're distracted with her primary you can ruin their day pretty quick, and most people won't notice the energy balls sloooowly heading toward them if they're already dealing with something else.
And like I said, spamming quarter-second charged energy balls into a crowd or a doorway, while not doing near as much damage obviously, is super effective since it's unlikely everyone will be able to dodge all of them.
Poll