Corona can do the same, and it definitely helps.
The other problem however is, that, as far as I understand the scene settings, flickering bright spots are actually correct.
If you have a lot of complex geometry (grass) that is highly reflective (mirror-like), then it is pretty much exactly the same as when you look at a road covered in broken glass on a bright day.
We don't have that many bright days now, but the ball season is coming, so maybe a better yet example would be a sequin dress like this:
Lot of tiny reflective surfaces, whenever anything moves it will flicker. And, thinking about the dress, I guess everyone will agree this is what should happen on it. Now if you model grass that (from distance) it looks pretty much like this, it will (and should) behave the same. Bottom line is, physical grass is not highly reflective, so neither should be its material in physically based renderer.
(I know it has been fixed, but I like the explanation with sequin dress, so there)