Thanks for the info, may help out a few newer pirates out there.
I have actually never seen a "Grenadier" actually throw a grenade in the game, what you define as a glitch, is how Grenadiers have always worked on 3 different gaming machines I use, all with extreme high end videocards, and full detail. Hence I have never found that running around to avoid the grenades to be of any use. Kill them fast, before they kill you. I also have not found that any of the certain hex's or weapon types designed to diminish thier attacks, etc that appear to work on them.
Witchdoctors, Gypsies, Brinescum, Mollusks, etc (any enemy using voodoo)
Use hex shot to drain thier voodoo, and they will be unable to fight back.
Enemies that utilize Voodoo, and Grenades, work pretty good for leveling grenades, since they do not constantly move, and will remain a distance from you (safe range for grenades).