well, nades are in-game entities and therefore not protected by client-based hit registration, like hitscan guns. if your ping is 100ms higher (50->150) you will HAVE TO lead your targets by extra 100ms; this is a very long time when trying to score direct hits at dodging opponents
while arty burst rifle can be great snipe-a-like peek-a-boom, the artillery will be significantly slower deployed, and thus easier to dodge. fletcher is definitely the worst, as not only you have to lead targets more, you also have to hold off on detonation by that extra ping.
if you regularly play with high ping you may indeed see success with some particular strategies, but a flank by a decent player and you lose half HP before you even received the first hit indicators