I played hardcore back in TBC and early WotLK doing most of the server firsts. Back then boss fights like Kael'thas, Vashj, and even Malchezaar pre-nerf were epic fights. Blizzard had to tune down the difficulty in the next expansions to cater most of the player base. The fights aren't challenging anymore unless you have a guild that runs heroics.

In ARR, the dungeons are very challenging. I enjoyed the steep difficulty curve after Brayflox. Primals and coil gave that epic feeling that was similar if not better than the TBC dungeons. I look forward to what SE has to offer in the next patches/expansion.