Neither the Raptor nor the Indra are one-shot-one-kill rifles, and that's why I carry them as my anti-Cerberus and anti-Geth snipers (at least for all classes but the soldier and infiltrator; I go with the N7 Valiant there). Given all those damned smokescreens Cerberus uses and the fact that both factions have cloaked units, I want a sniper rifle that's effective at medium range on rapid-moving targets without requiring a concentration mod (I prefer using my second slot on a piercing mod rather than taking the time to mail slot Guardians). In that case, being efficient with ammo is less critical than being efficient with time; I don't care if it takes five or ten shots to down the guy if they come flying out of the gun in less time than it takes to accurately aim and fire off one round from a more powerful gun, especially if it means I still have enough bullets to kill two or three more enemies before reloading. Having 15 or 25 shots on tap also means you spend less time aiming and more time shooting; granted it takes your overall accuracy down but you can afford to miss shots. As far as accuracy, most of the sniper rifles are about pinpoint accurate; it's just the muzzle climb on the multi-shot weapons you need to be concerned with. The way to compensate there is to eschew headshots and aim for center of mass; the recoil will walk the shots right up to the head. Reapers on the other hand get the one-shot treatment - they don't have cloaks or smokescreens, move slower, and to me at least they seem to field armored heavies more often. It's helpful to have a gun that can drop an oncoming Brute with one bullet.