I actually think flash grenade is pretty nice because if you get hit by one but are situationally aware, you can retreat to cover while blind and not get slaughtered.
What I've seen so far is that if you panic when struck, you're dead. You're basically say "I can't see, shoot me!"
they should add an effect to flash grenades were it makes doritos appear all over your screen so you can't just q spot through it and aim for the dorito. i do quite like flash nades though, if more people used them they could be a real nuisance!
They did recently get a slight buff. Although, they need something else. I was thinking maybe changing the hitmarker. It could show two different hitmarkers, one for when it's just a hit and the other for when it's a 'blinding hit'.