Legendary items supports NpcSpawn npcs. It will create a drop bag with the loot inside at the position the npc died.
It relies on the Loot source being set correctly, and allows you to filter based on the name of the npc profile.
Example config.
{
"Loot source": "BetterNPC",
"Prefab shortname, boss profile, event name [null if not required]": "name_of_your_npc_here",
"A list of required skin IDs [null if not required]": [],
"Identifiers to exclude from consideration [List - null if not required]": [],
"Drop chance [%]": 10.0,
"Should we consider loot chance modifiers that the player may have?": false,
"Items that can drop from this source [profile name: drop weight]": {
"Rocket Barrage": 25
}
},