Incursion Scarab of Invasion barely seems to work

Testing on Strand maps, i ran through the maps looking for packs and counted the total mobs in each map using the Map Device. I noticed barely any difference in mob count both with and without scarabs.

When using the scarabs, I also regularly only noticed 1 pack that actually had monsters from Incursion even when using 3 scarabs, which doesn't make sense at all.

It doesn't seem like it is adding anywhere close to the amount of mobs that it says it should add.