When using armamentarium in PVP you lose the additional grenade charge entirely upon death which seems to defeat the purpose of using the exotic at all. Same happens with Spirit of the Armamentarium in the exotic titan mark. I tried searching both the forums and TWABs for any mention of this being intentional but did not find anything that points to that being the case. If it is intentional it would be nice to have this information somewhere IN-GAME.