I actually have to change my earlier stance and say that the number of nades isn't the problem, it's the timer.
The way it is right now, it takes virtually no time to throw a grenade...but even if your opponent rolls away when the grenade is thrown, he will probably take significant armor damage from it. Even if he doesn't, it takes less time to throw a nade than it does to roll away from one - so by throwing a grenade your opponent loses nothing but a quarter second of shooting time, and in return he gets at least a second of free shots on you while you try to roll away, even if the grenade doesn't do anything.
Grenades, IMO, should be something you use to dislodge people from cover, punish devastators, or force people into moving where you want them to - not just a general purpose winbomb. Reducing the number of nades wouldn't fix the problem, it would just make it less noticeable.
Relic should just increase the arm time on the grenades (time to explode after landing) by 1-1.5 seconds at least. Devastators may need a slight health nerf to compensate (as nades are the primary devastator counter) but I think it would improve gameplay a lot.