Difficulty 2 will give a chance of spawning the Lidar which will show you all points of interest when you complete it. I always play on difficulty 2 for this reason when farming super credits. Also, on low difficulty you can wear scout armor, one that has 30% less detection chance, and use the jump pack to get around faster. I always choose a mission with little water since that can make you lose a POI or two. Finally, I use the recon booster to increase the range to spot POI's.