When Molten Core was first released in Season of Discovery, there was a bug that allowed players to enter the raid with parties of more than 20 players. Since players could enter other raids such as Azuregos, Lord Kazzak, and Onyxia's Lair with up to 40 raiders, players assumed that this feature was also available in Molten Core. Unfortunately, this turned out to be a bug and not a feature.
Molten Core Overview Guide — Season of Discovery
About one week after its release, Blizzard reduced Molten's Core's raid size down to a maximum of 20 players. Many raiders were upset with this change, stating that they would now have to bench some of their Guild members to fit this roster. However, after receiving this feedback, it appears that Blizzard is looking for ways to add variable raiding to Season of Discovery's future phases.
What do you think of variable raid sizes coming to Season of Discovery? Would this allow you to bring more of your guildmates into future raids? Let us know your thoughts in the comments down below!