As I was testing them, I noticed the enimes were not dying.
It appears that Giant mantises, Fire ants, Coyotes and Fearl ghoul roamers are 100% immune to explosive weapons.
The Weapons I tested were Rockets red glare, Mercy, GMG, Thump-thump, 25mm APW, Grenade Launcher, Grenade rifle, Esther, Frag grenades and Anabelle.
Has anyone else encounterd this bug or knows of a fix?