I actually don't have Eternity Eddie at the moment
I sacrificed him last sac event and bought one to sacrifice as well.. figuring I could just buy another one in a few days... before realizing they put a cap on the number you could purchase with FC... So I've got to wait to get Eternity Ed again.. dang it.
Dark Clairvoyant pretty easy with Van Helsing, Darkmoon Lilith, Lucifer Morningstar, Clairvoyant
(Biggest issue is Dark Clair self-granting Endure constantly)
Prince Beelzebub figured out with Oni Ed (Alchemy), W LOL (Orbit), Lucifer Morningstar, Beelzebub (Frontier)
Prince Wrath via Van Helsing, Lucifer Morningstar, Darkmoon Lilith, Wrath (Starfire - only level 40) - May be easier with Oni Ed though.
.. haven't even looked at the Eternity Ed battle.
There are several "extra" attacks from the bosses. Prince Wrath hits.. then does 2 more extra hits of true damage.... Prince Beelzebub basically always reflects damage...without shields.
These are defiantly end-game battles.. I'd be really bothered if the achievements weren't low, at 30 runs needed each.... but still.. even 30 is a chore to a degree. I hope keys drops from elsewhere eventually. The cost of the keys is the largest downfall of these dungeons.