Yeah, but I was at the top a lot with the Volt, so if anything those matches demonstrated that the Volt is overpowered, and yeah, in the same match you were using the EVA I was using the Alternator and struggling for some reason. Sometimes matches go badly, lose a few 50/50s and you don't build momentum for your boost / Titan etc. then it can be harder to recover from. The weapon doesn't cause that though. With that said it must be harder for you American's since I often put us on UK servers. Also, the people we play at 4am in the UK are far better than most in online lobbies. That Shadowlegion guy was probably the best player I've seen on PS4.
A lot of those people we were with also seemed to be getting to grips with their guns and whatnot, using guns on our recommendation, so they hadn't formed a clear opinion on their favourite. Ultimately though, I think because of the time to kill is pretty low. I imagine you could have done very similar to what you did with the EVA with the CAR, Volt or Alternator also.
I do think that there are better guns, but I think that among the better guns it doesn't matter all that much which you use, the difference's aren't so stark that they will cause you to lose your one versus ones. The R201, Volt, EVA, CAR, Alternator, Hemlock and G2 are all useful weapons where their differences in time to kill are not stark enough to make any one of them significantly more valuable than the rest.
It's more about consistency than anything. Weapons like the Flatline, and a number of the LMGs are fine but the random horizontal recoil makes for rng based kills / deaths. Others are clearly in the game just for the fun factor. Projectile based weapons like the Masstif and L-Star are bad because the bullet travel makes aiming harder, reduces the time to kill and also means you might be killed before your bullets even land on the target. Same for grenadier weapons like the EPG, while snipers are too situational to be useful in these relatively dynamic battlefields. They're all fun to use though, so they don't really need to be balanced.
In some ways making these weapons underpowered is a good way of allowing them to be enjoyed within the game without influencing gameplay in a negative way. If snipers and light machine guns were much more effective than they are, the typical gameplay and match flow would suffer. The same would be true if everyone was using grenadier weapons because they were incredibly effective, it wouldn't be all that much fun being killed by that after a while, but as it is they are a fun novelty.
As it is, the lack of skill based matchmaking makes even these traditionally low-tier weapons quite fun to use. I have been able to top the leaderboard in games of attrition with the Coldwar and EPG, despite my feelings that those are the worst weapons in the game.