These NMs are known to be soloable by a 75 DRK, MNK, SMN, DRG, THF, BLU, BLM, NIN or RDM, but it is suggested to do this fight with a healer and a sleeper. A RDM can easily solo these Spheroids without Utsusemi; Phalanx and Stoneskin should be enough.
The NMs are susceptible to Lullaby, but build up resistance fast. Each casting of Lullaby lasts 3 seconds less than the previous one, and eventually they just resist entirely.
When the NMs are defeated, check the gate again for another cutscene.
Cardinal Mildaurion is somewhere in Jeuno, and Ulmia is desperate to find out where she may be hiding. Perhaps the three "high-ranking" Tarutaru "officials" know something...