I was underwhelemed by the Sniper Rifles in ME3. They really toned down their effectiveness.
The Geth Shotgun is still beastly, and all the sniper you'll ever need, lol. It's not 100% accurate, but DAMN accurate at long range. One of the three 'bullets' will tend to hit their mark at long range, and still deal devastating damage. If more than one hits, it's almost a guarantee to kill whatever you're shooting, lol. You don't even need to charge it up. The damage is that ludicrous.
Honestly, if you use the Chakram Launcher from playing and 'beating' the KoA:Reckoning demo, you don't need a sniper rifle. That AR is just stupid strong. Like broken strong, even in Hardcore. I chose a weaker AR on purpose, because the Chakram Launcher was killing things too damn quickly. The 'discs' attach to an enemy and explode. When you pump an enemy with a clip of those discs, yeah... they die.
I have to say, I REALLY felt bad ass when I used that Geth Javelin Sniper Rifle (the one with a delay before it shoots). The sound coming off it gave me shivers. It's SOOOOO awesome. None of the snipers are that effective in comparison to other weapons, but that sniper was still fun as hell to use, and strong for a sniper. Easily the coolest weapon in the game for me. The scope was one of a kind, and the sound effect just makes it sound like it can kill a thresher maw in one shoot.
One tip for other ME players... NEVER equip weapons you pick up on the field once you get them. They'll be less effective than whatever you currently have, assuming you maxed out the upgrades (which is pretty much a guarantee after the first few missions, unless you're upgrading everything you find)
What I do is wait until after the mission, go to the Citadel and test the weapons out in the firing range and see if I like them, THEN upgrade them.