It looks like the Thermal Overload perk, which adds Overload to Solar and Stasis grenades, doesn't work on the Duskfield grenade. After hitting an Overload Minotaur in the face with one [i]three times[/i], I had to quit the Perdition legendary Lost Sector because it just doesn't work. The feed doesn't say it was Overloaded, it doesn't slow down at all, and it just slaps me in the face without caring at all.