Malfurion wasn't physically inside the Dream until after the events of Stormrage. His body was kept in Moonglade, where the priestesses of Elune would keep him alive from blessings of Elune. There's also a moonwell directly above the Stormrage Barrow Dens, where he slept.
Worship of Elune could play a part. We've seen a few times in lore that different elves used different means to maintain their arcane addictions. The Shen'dralar Highborne siphoned energy from a demon in order to survive. High Elves meditated and used enchanted jewelry in order to survive. The Moon Guard had wells of arcane energy all around their stronghold. Who knows what Jarod did?Jarod lived in isolation for thousands on years and he was doing fine except that he lost immortality. It does not follow that they place it every where they go, so they are addicted.
Moonwells need several different things in order to function, it seems. In Suramar, the druids say that they need the blessings of the local animals. In Shadowmoon, they needed a piece of Draenor's moon to invoke Elune. But, they also seem to have arcane energy - before the Cataclsym, the visiting Highborne and a temple guard had this exchange:
They most definitely have arcane energy inside them. If Night Elves didn't need arcane energy around them (in some form) to survive, then there would be no reason for the creation of moonwells in most zones they spend lots of time in - even Stormwind, the Firelands, Northrend, Ashran, Outland, and the temporary camps in Ghostlands. What other reason would they need to create them? They pray to Elune with or without moonwells, it seems.Archmage Mordent Evenshade looks over at the moonwell with a sigh.
Sentinel Stillbough says: Take your gaze off the moonwell, exile. The power within is not yours to wield.
Archmage Mordent Evenshade says: Calm yourself, Sentinel. I do not seek to use it. I am merely... remembering.
Sentinel Stillbough says: Recalling your treachery?
Archmage Mordent Evenshade says: Enough. I have been apart from this for centuries. The well within this temple may be a pale spectre of the Well of Eternity, but it still holds the same... beauty. Purity.
Archmage Mordent Evenshade says: I had forgotten.
Archmage Mordent Evenshade says: I do not believe admiration and wistful thoughts are against the societal norm.
Sentinel Stillbough says: Watch yourself, Highborne.
Archmage Mordent Evenshade says: You were the one who challenged me for merely looking. I still await my audience with Tyrande.
Sentinel Stillbough says: In good time.