Dropped grenades should not glow unless the pin is pulled… Instead, they should be more colorfully pronounced (i.e. frag color should be more ‘green’) to help players see them as pickups on the ground. This might not even be necessary as they already contrast with the ground decently well. This is how Reach worked and it was very obvious as a gameplay mechanic. I feel like a silent majority would agree with the glow being weird as it currently is, everyone I talked to said it was strange and they cannot tell if it is a primed grenade or not when it first drops.
The mixing on grenades could also use some work, the current sounds and mixing hardly stand out from the chaos. Again, play some Halo: Reach. There is absolutely NO mistaking when a grenade is thrown in that game, and it is immediately obvious where it is, when roughly when its going to blow up—all just from the sound design.