Qeynos Badge Quest #2 - Way too many undead spawned

[Daedalon]

I was doing the Qeynos Badge Quest #2 when the two NPCs spawned by the stone ring got an inordinate amount of summons (I'd say approximately 100, not even joking) and proceeded to decimate my pet, myself, and 1 of the 2 other players that responded to my OOC call for help. I attached a screenshot here, but many of the creatures are stacked in the same space; it may look like there are only about 12 or so, but there are far more!

The only thing I did that might have contributed to this was stand on the hill with the investigator for about 2 minutes while I summoned my pet, then buffed it and myself a bit before descending to engage the 2 NPCs.