Mercs can be beaten, but beating it with special builds and OTHER snipers isn't the best way to go about it, this is why snipers are so hated in many other games and so much time is spent designing new mechanics to make it easier to counter snipers (like TF2's kill cam showing you where the Sniper's hiding), you don't want the game to consist solely of snipers and those trying to kill them. Rock paper scissors is actually a horrible thing to compare a video game's balance to for anything that can't be changed mid-game, I mean when's the last time you had real fun playing rock paper scissors? It's an example of something that's balanced but not fun, you're just as likely as your opponent to pick a hard counter but its mostly luck whether you pick what your opponent's weak to, you're at a disadvantage over something other than skill.
It's more tolerable in a game like TF2 (the engineer/spy and spy/pyro relationships) because you're one of many players and you personally dying to one person on the other team doesn't matter much, especially since you can swap your class whenever you die. There's enough players that the rock paper scissors relationship become a contest to see which team can better balance their team to fit the situation. In a game where you're committed to a choice for the duration of a match or save file (RPG's are the worst place to have rock paper scissor balance by far) it feels cheap, that the player who just beat you won because of something beyond your control. You just kind of accept that you're going to lose to worse players because you picked the wizard at character creation and they picked the witchhunter, not fun stuff.
That being said, I think the issue is more with the maps than any real fault of the Merc. We're flying huge, relatively slow-moving ships in the sky where you generally aren't going to find much of anything other than clouds and the occasional mountain. Those are the perfect conditions for sniping and if military airships were a real thing they probably would be all about the range, we see this in science fiction with starships all the time. The only thing working in our favor is the setting's limited technology and low altitudes. On Dunes you spawn in the open with nothing to put between you and the enemy snipers. It'd be nice if there were more maps like Canyon, with lots of cover and little opportunity for sniping. Things are densest in Desert Scrap but I've yet to meet anyone that actually enjoys that glitchy campfest. If it weren't for that achievement...
