Like many, this boss annihilated me and my group the first time - but that's what I loved about it. Meanwhile, the other (Hard) dungeon was a totally blind and near uneventful success. On entering the Burn a second time with an experienced group it was a one-shot, yet the boss still maintained enough 'oh no' moments to remain fun. As with any encounter, just a matter of learning. For the mist phase where he's going to charge, the best approach is to have people in different corners (away from eachother), typically at diagonal angles seeing as the AoE's tend to go horizontal and vertical (through the center) mostly. By being split up, you ensure people are always free to unroot anyone caught in the AoE for any reason - all it takes is a ranged poke of any description, even a WHM Aero 1 does the trick. Clumping up together and getting unlucky is bad-news-bears.

TLDR - No, this isn't a 'hard' fight, it simply has more factors to be aware of, and being relatively new means not everyone is used to it yet. It's also less forgiving if people take the mick, seeing as people can get rooted simultaneously and/or acquire major damage DoTs and/or eat continuous rime AoE at the worst of times.

In short - love it. Definitely my favourite of the two new dungeons and fast becoming a favourite in general. First time I got to soak in the view after leaving the underground section was delicious.