You usually need to land all pellets unless you're using a max impact shotgun at REALLY close range or a final round. You have to be precise to land all the pellets. Invective is good because by firing twice quickly you don't need as much accuracy. But that's why it's exotic. Also, zoom while ADS on ANY weapon multiplies the range. That is working as intended. Obviously it doesn't do much for shotguns but it still helps.