Both. And regardless of perks, damage inconsistency is a problem.

Perks matter a lot. Proximity grenades and blinding/concusion both decrease damage making it less likely to get a 1 hit kill. Also GL are not hit scan so internet latency/speed and connection to the host all play factor in hit detection and damage.

You’re missing the point of this.

The point is there are a lot of factors that affect grenade launchers, so really your missing the point. I'm just trying to give you advice to reduce the inconsistency your experiencing.

Oh sure, because it’s totally fine for grenades to bounce off of enemies, go through enemies, and constantly change their damage for no reason.

Most of that sounds like connection issues. Since your most likely going for mountain top my advice is rely mostly on heavy grenade launchers, farm out a play of the game from shaxx that has blast radius boosting perks and masterwork, range finder is also nice. Prospector and anarchy are also really good as you can set traps in door ways, halls, small rooms and lead enemies to them. For lightweights dont use energy launchers as they deal less damage than kinetic, so farm out a militia's birthright with max velocity and spike grenades. If your a warlock use fighting lion and well of radiance with lunafaction. Typically dont go for direct hits as usually you'll miss random things will happen when it hits a guardian, like it bouncing off.

Not everything can be blamed on connection issues. And no, I don’t give a rats a** about mountaintop. Just because I made a post about grenade launchers in PvP that doesn’t this has something to do with Mountaintop