Yes, fractals of the mist are the primary challenging endgame content at the moment. There is also the living story that provides a story based endgame, with multiple instances to progress through and unique rewards.
The 2nd season of this story is about half way done, with the second half starting back up on Tuesday.
If you want hard repetitive content then fractals are what you should look at. If you want story driven content then the living story is what you should look at. Additionally there is currently a developer based discussion on raids coming to GW2 in this forum, which probably won’t be implemented for another 9 months or so, but it is something to keep in mind for the future.
