Board Thread:General Discussion/@comment-8883075-20140506055205/@comment-24844464-20140507041547

That's what our writers wanted. Without the Witch of the East, Glinda wouldn't be able to tell Zelena about all the factors creating the most magical power in Oz and help her back to the good side which was not succeed. Therefore, Zelena got enough ingredients to enact the spell which can change the time stream but being killed by mr.Gold.

And sometimes some characters' appearence may not necessary. Just like in Beauty and the Beast and as for Rumpbelle, although in Quite Mind, we've seen Lumiere a.k.a the Candelabra , but Cogsworth ,  Mrs. Potts and Chip never appear.