Nice! 
If you placed Elemental storm or Ultos on mortar instead of reckless tempest, multiple instances could stack their DoT if a different mortar created them (not the debuffs, just the DoT damage)
@grey-maybe explains it here: [1.1.9.1] World Police and Friendly Fire - 5 Guardians of Empyrion Paladin [4.20 Crucible] [SR75] [All Celestials] - Grim Dawn / Classes, Skills and Builds - Crate Entertainment Forum