you only need to hit them with 1 scoped shot to 4sk them. the other 3 can be unscoped, assuming all the bullets from the burst hit. given that the lr has a lot less aim assist than the dmr, it's just easier to use the dmr and get similar results anyways. lr is a lot of fun once you get the tricks down though
I like yourself, wanted some variety and gave the light rifle a go. While it did get the job done, it not being "hit scan" is a deal breaker and I leave it to collect dust. Tried the cuvvy carbine rifle and enjoyed the fast fire rate, but it just doesnt pack any punch.
In the end, I've just settled on using a loadout with the DMR and Battle Rifle with the firepower ability. They both are strong guns and plenty of ammo can be found to keep you rockn and rolln. I just rely on ordinance drops and map ordinances to keep it interesting.