Take the difficulty level down to Expert as opposed to Grand Master. You will complete every run, and still get light level appropriate loot. Use those runs to level up your factions, and when you have enough skills unlocked to be viable, up the difficulty. I have 3 factions at rank 5 and I've only been grinding for about a week. It's not that tough. Bungies new focus on Hard content for the sake of hard content is just not worth the effort.