I use them mostly on raids, use them to finish off pretorians in VoG quickly. I run a scout rifle mainly so if something gets too close for me to be accurate with that the shotty is a good backup plan. I am apparently part of the 1% that likes using a shotty on a regular basis in PvE apparently. Snipers do give them a pretty good run for their money in 90% of the scenarios you are in though.