I was blown away by the animation in this episode! God, I LOVE Madhouse! If only BONES and Madhouse did a collaboration together, it would be the best anime ever.
IMO, I think the specialist category is a convenient plot device the mangaka (Togashi) slotted in to open up more possibilities for future characters with unique abilities. It's also a smart way to cover your tracks because if he didn't, it would be just bad storytelling if the protagonists encountered a new type of enemy and their enemy will be explaining this specialist stuff all of a sudden. Additionally, it would make Wing and the Hunter organization look like a bunch of incompetent chumps if they can't classify their own/all powers in this universe.
I'm not too sure about this, you guys, but I'm really enjoying these naked and disturbingly erotic Hisoka scenes. They're extremely hilarious and I simply can't get enough of it.