I know how effective the grenades are, I also know that the enemy don't have their guns up while throwing the grenades. Plus a good flashbang will make them toss the grenades into walls. Tripmine will kill all three of them if placed right. Lightning grenade will keep them at bay or kill them for you to counter attack. Magnetic and fusion grenades will tilt slightly and kill them in one hit. Incendiary grenades can catch them on fire too. Swarm grenades will home in one the target and deal more damage. There are plenty of ways to counter firebolt and arcbolt grenades, if you haven't found them out then obviously you would cry for a nerf. Mostly everyone resorts to that as their first choice of action.