Before 6.2 went live, there was a blue tweet hinting that there may be multiple shortcut quests. The first, Well of Souls, requires you to collect Soul Remnants from Gorefiend, in turn teaching you the ability Soul Conduit, which teleports you to the upper level of HFC, right after Gorefiend.
If you look at Wowhead or WowDB, you'll find Normal/Heroic/Mythic versions of Fel Essence, an item analogous to Soul Remnants. In addition, you'll find the spell Fel Conduit, which has flavor text reading "Attunes the target with fel energy, allowing Khadgar to offer direct teleportation to Mannoroth's platform in Hellfire Citadel on Normal difficulty." (versions exist for Heroic and Mythic as well)
However, there doesn't seem to be a quest linking the two like Well of Souls does for Soul Remnants and Soul Conduit. Does anyone have any further information on whether or not a second shortcut quest exists and how to access it?
Apologies for being a new account and not able to post links yet.