Moongrave Fane???

[Tasso]

Is this dungeon the hardest one in the game... because I find it impossible with dungeon finder. Iv been through so many groups and they all stink hot poo?!

[Dubsky]

By far no the hardest, just "tricky". If you don't know what's going on, fight will get harder and take an endless amount of time.

I wouldn't queue for DLC dungeons if you're looking for a fast or atleast nearly clean run.
Always ask friends or in a PvE guild.