I totally agree with you at some points. But most of the sniping players in here are simply holding down the RMB on Outpost, or simply don't always hit their first shot. You can avoid getting shot most of the time, by moving unpredictably. I do it like this: If the sniper hits me one-shot and I'm low or he misses, simply push him as most people dont immediatly switch to their secondary. If you die, you die. 50/50 just like every gunfight in IS. Plus you most likely get traded immediately afterwards. And sniping itself takes a toll aswell. Miss your shot on close range/mid-range and youre done for.
Back to the topic: LMGs are nonsense in this game. As cool as variety is, nobody plays an Ultimax or the PKP in search and destroy for example. These guns have no purpose whatsoever. Sure, decent damage, big fat magazine, but low DPS. Ironsight is a game of kill, run, kill, run. You can't run and reload your LMG once it's empty. It takes rather more than 3 seconds to reload it, which can be crucial in a.) the fast paced game of ironsight itself and b.) rotation and speed based gamemodes like TDM. Not to speak of the smaller maps.
I find the ARs perfectly balanced, except for the ar-57, thats about it. I have no complaints about the smgs, cause they fit the game perfectly fine. Quick reloads, gunfights less than 2 seconds, quick rotation and you're always set for the next opponent. SMGs could use a damage nerf though.
Regarding to your last point: Well, what does one expect from a game which genre is years old and sees no change whatsoever? FPS games in the end all look the same, but there's always different levels to it. COD for example features a replay mode, alot of gunpatches, bugfixes etc. And the variety of guns is way larger than this game offers. Ironsight needs a catch to it. Something that appeals the player other than the gameplay. You can't compare it to cod, cause its a way different budget into it, but imagine Ironsight having a campaign, more depth into the story, an actual loading screen, a tutorial for you, an intro the first time the game starts, more visual effects, weapon customization (visual), a simple shop, killstreak (30+) rewards/medals, full public stats, ONE currency, maybe two. That's alot of things that Ironsight could use to make it more unique to the player. Sure a campaign won't affect the multiplayer, but lets be honest. It gives the game depth and keeps the user interested, other than just logging on, searching for a game andgrinding for a gold camo which costs an incredible amount of money for the free-to-players which they could've used to buy different guns/equipment with.
In the end, this game's only a year old. I hope to see alot of changes being made in the future, especially regarding what you've spoken about. Sorry if I branched out a lil bit, but I couldn't hold back