that is RNG for ya, i have farmed Legendary Sectors before all day and had no drops, other days only took a few runs. when I'm on a dry spell i will go run other activities for a bit then come back, or swap characters for a few runs then swap back, and as far as the mods go, Make sure you ADS your Sidearm until the Unstoppable shot buff procs ( takes about one second), and if auto rifle barrier is not cutting it, try the Scout rifle anti-barrier mod, or and exotic that has it built in, also barriers cant put up a shield if they are frozen.... tons of things you could try

Another player who doesn’t know what the “R” in “RNG”stands for. 🤦‍♂️

I mean, it takes 4min tops to clear that legend lost sector. So 12 clears is under an hour. I've heard stories of people farming 3 hours with nothing to show.