Just spent around 45minutes switching between groups to test this boss on PTR. It's extremely fun, i played a rogue and its quite enjoyable on that class, lots of movement and target switching though so maybe i shouldn't like it as much as i do right now. We got the boss (or 1 of them) down to around 26% and the others around 50% but id seen the fight so decided i'd get some sleep.
Other people's thoughts on it?