Mobs such as Any Foam based enemy, Slimes and Ghouls aren't affected by looting, however Hollow Armors are affected and drops more items accordingly to the Looting level of the weapon.

Tested with Looting 255 Diamond Sword, Slimes still drop 1-2 Gel while Hollow Armor drops 7 stacks of Strange alloys.

Mod version 1.2.6