Ok.
First things first, 3 Point Sling has one major setback. It requires a mod slot to be equipped.
I'd rather use a different third mod on my JG or N-TEC just because I don't see 3 PS being that good in most situations.
It also only helps massively with heavier weapons such as Alig or HVR, but still - it takes up a slot.
Second things second, Grenades are fine > Players that use it as their primary engage of attack aren't.
Also, Explosive weapons are the ones that should get nerfed here. I mean.. at least the OPGL and Osmaw. EOL in comparison is just a joke to OPGL.
If you're really good with hitting your OPGL shots I can confirm that everyone you'll go up against will automatically hate you. It's so easy to just hold a point from somewhere, not to mention that the grenades can kill you instantly if you're in around 5 meters of the explosion.. also the AOE of the grenades OPGL has.. sheeeeeeeesh. It's very big. Hard damage / Vehicle Damage is also enormous not to mention the fact that they 1 shot nearly anyone.
OPGL is OP in offensive and defensive plays since, with the correct trajectory, you can 1 shot anyone without needing an angle or teammate.
In other words, OPGL is a good weapon with an insane skill ceiling, but it's maybe - most definitely too good in most scenarios.