I don't actually think the locations we see in Coil are the swords/spears. The craters at each of the Coil entrances (there are two others already in the game if you look closely) are made by actual chunks of the outer shell. The swords/spears are much much larger and few are actually anywhere near playable regions at the moment... only one I can think of off the top of my head is the one just on the edge of Mor Dhona.

I have a feeling the objects impaled through Dalamud will serve a greater purpose later on, especially since they seem to be directly linked to the Twelve (there are twelve of them and each represents one of the 'gods' as shown in the End of an Era video).