I've finished all the classes (unlocked everything), so I can say that I pretty much "completed" the multiplayer.
I'm just gonna say one thing, this is the best online FPS I've played since Ostfront. This game will change so much in the future years. People will undoubtedly compare Frostbite features to the other games.
BTW about everybody being snipers, I think it's the easiest and well equipped class to play. The sniper rifle is the only one-shot weapon in game(with headshots, not talking about HC), you can easily pick off infantry and rack-up a nice K/D ratio. I usually suck at being a sniper but yesterday I racked up a nice 50-2 K/D while I was on my unlock run.
You have a Mortar so you can take-on armor and blobs of infantry, or even help defending/defusing crates by calling it on it. M1911 can take-on any infantry close range, and you will come on top every time if you fire first.
Another thing is you don't have to do any teamwork. You don't care when they set a charge on M-COM's, it's infantry job. The only incentive is to throw Motion Sensor's to help infantry. That's why Snipers are generally hated, because they're not teamplayers. I too think a sniper is a "waste of squad spot" sometimes.
Though that being said, I think it's entirely possible to keep up with infantry rather than sitting back. I've had games where I was fighting alongside my squad, picking out the distant targets targeting them while they took on the closest ones. So it's possible to be a "teamplayer" but most snipers usually prefer to sit-back and eat chips while they snipe
Still, Engineer is my favourite class