DCUO is a prime example of how making everything too easy that everyone, even joe casual 1 hour a day, will finish things too quickly. The game died within months.

Whether you want to argue if this is endgame or not is semantics. This WILL be endgame for however long it takes to put something new out. When players finish things too quickly it means they stop playing your game. If you don't balance it to where the player keeps reaching for that carrot on a stick, your game will die. It's how MMO's have operated for over a decade, WoW included.

Reserving judgement until I see the dungeons themselves, but it's not looking good from an outside looking in perspective.