User blog comment:DeathGodPrayer/Talk About What You Want!/@comment-82.178.91.153-20140209043700/@comment-1359322-20140209045726

That's part of the reason for Lord Gremory and Phenex not appearing.

Well originally even if they kept the Angel instead of Irina, it would still be fine since the Angel never spoken even in the LN. They changed to Irina because they changed the fight.

Well i'm just saying that there is a possibility of Venelana not appearing because the anime could change it to something like, Grayfia saying that she received an order from Venelana to train Issei, while Venelana wasn't shown.