Okay. For a moment I'm going to put aside a very important fact that everyone here is emphasizing: that you are being trolled by a small groups really annoying and unsportsmanlike conduct while you are a player that 100% always acts in a very annoying and unsportsmanlike manner, and because I'm bored at home because of the virus I'm gonna write a long and descriptive post about this.
From what you wrote I'm assuming we're talking about FAIK....I mean that unit I call fake. First lets get this out of the way, NOBODY likes those guys, I mean in this entire game there's probably 2-3 players that would ever defend them when people are sh**ing all over them in a conversation. Fewer than would defend you with your parasitic, unsportsmanlike gamestyle that's based around not allowing the enemy to shoot back at you (you must see the similarities).
Now, here's what's happening when you see that d***head 3-5man on the enemy team and why what they do works (sometimes). You may see them with ERLL, laservomit, gauss, etc but it's always the same. Their entire strategy is based on a few things. 1). Synchronized mechs 2). Defensive 4v1 trades 3). Incompetent enemies 4). Enemy getting bored before they do
1). Their mechs are completely in sync 95% of the time. It's been a long time since any good units in FP force their players to drop specific mechs/loadouts. It's just not fun, and everyone does their own thing. Now most people that can play know not to bring completely dumb things that make 0 sense, but still, when one side has all laservomit mechs, and the other has some laservomit, some dakka, some gauss, some atms, etc. The former side tends to have an advantage, it's boring, but that's how it is. Primus tells them what they're taking, and they're taking it, no fun allowed in fake.
2). They will find a position close to their maximum effective range and will setup all their mechs there and wait. Sometimes because of the map, that position is a strong map control spot, sometimes it's some hill at the edge of the map nobody cares about, and sometimes it's the edge of the map behind the spawn slightly elevated above spawn walls so you can shoot over (plus they get you to go through dropships to get to them #tactics), sometimes it's the basement in HPG or garage on river city with HGR mechs. They can wait there for the entire duration of the drop, but the idea is that most players will try to slowly advance when they face no enemies, sooner or later people will poke into their 4-5 man firing line, and they get melted. This is not because they are good players, this is not because they have better aim, or reaction time, it's simply because they will force you into a 4v1 situation where they've pre-aimed 4-5 mechs at the most logical spot where you'll be coming from.
3). The only reason their crap works is because generally they encounter players that can't get around their bs. I can't really remember any drops I've ever lost to them with a comparably sized force, and the few times we lost it was always because our pugs would lose patience and feed their firing line one by one. Their entire tactic is based around the fact the enemy is worse shots than them, they lack their map knowledge and ability to do approaches based on it, and are less patient than them. In the 4-5 erll mech example, they get totally wrecked by 4 competent players with ppc poptarts. In fact they even lose to 4-5 good players with erll mechs who trade into their line, because only 1-2 fake pilots are actually good shots. But most players dropping FP don't bring erll all maps every mode because it's boring.
4). This is the big one. They will setup in a position that is favorable to them, even when it's a useless position nobody needs to go to, and they will wait. If they have to wait the entire drop there they will, because they're cowards. They're the most cowardly group in the game, they will always que on siege defense, never attack (except when we troll them forcing them to switch sides and then they don't ever come in the gate). This type of approach is entirely based around PGI not enforcing the dragging out the timer pointlessly rule. They setup with 5 ERLL mechs on some hill at the edge of the map? You have brawling mechs? There are no approaches to their position without getting hit by 20ERLLs? No problem, you can completely ignore them. They still have 7 mechs on their team who are also not looking to sit and do nothing for 25 minutes, sooner or later someone on the enemy team will say f*** this and come fight you. When their 4 man is losing to another 4 man, and they all fall back behind their spawn trying to force those 4v1 trades, under dropship protection, plus after every death you have to walk for 7 minutes to get to them. When they are losing it is on them to attempt to move out and get the kill lead back, when they are not actively trying to do that, they are violating TOS, but PGI will not take any action against this. They will also constantly run away and hide at the end of the drop when they've lost to waste peoples time, but PGI will also not take action against this. It's very unfortunate that we are forced to deal with people who would rather waste everyones time, and are happy doing it, but that's how it is, they're not going anywhere. If TOS was enforced, this unit would be in a perma ban, but it isn't.
At the end, the problem you're encountering has nothing to do with ERLL balance against other weapons. It has to do with basically a small but very organized unit playing like total douches, and you're mostly seeing it in drops where they're not facing good enemies, because the usually get owned in those.
Also since they actively break TOS, since they don't care about winning, and will often intentionally take actions to lose in order to troll their teammates they don't like, etc. I strongly encourage everyone to troll the crap out of them when they're on your team. Might as well have fun with it, don't let them bring you down