The impact mods drop from the teralyst iirc, sweeping serration is a baro exclusive and breach loader comes from the razorback, which we just had on ps4, i know, but it'll return. Last but not least the 120% damage mods like breach loader, sweeping serration and collision course are something you could go after. They drop from hive missions, the corrupted vor in the void, and iirc correctly all of them are obtainable right now, which means you won't find any at baro ki'teer. The dual stat mods for shotgun are also pretty decent. It drops from high level nightmare missions, which are tough, but easy to master with a squad. Chilling reload, another nightmare mod, is worth a look at.
Blaze is a nightmare Mod I like, which gives you 60% damage plus 60% heat and thats nice. Point Blank and Hell's Chamber are absolutely necessary. The basic damage mods of shotguns are a go to in my opinion.
