I know when I jump on IA and decide to play as a sniper, the M320 or the Lynx are my first port of call. I do often consider sticking an SMG or something small in my backpack in the case I get flanked and need to move into CQB, but I often have a sidearm or an exfil plan anyway.
At the end of the day, your role is that of a sniper, you take a high powered rifle, sit a couple kilometres out and pick off the key targets, your not there to shoot every single rifleman you see on the field. You take a Lynx 12.7mm with APDS rounds, your kitting yourself to take on light vehicles and HVT's, you take a .408, your out there for the kills on the specialists in squads or the officers.
I do agree there is no reason for a rifleman to be carrying around a .338, they should be carrying a 5.56mm or 6.5mm rifle with standard attachments, the machinegunners holding the LMG or MMG and the marksmen carrying a 7.62mm, 9.3mm or .338mm DMR or ABR.
At the end of the day, its a public server, not a realism unit. We're here to all have fun, not simulate the military, if someone feels like they'll have more fun running an SPMG with a nightstalker etc and sitting a kilometre out, so be it.