Well, Judgement Chain can be used as an instant kill. By the looks of it, you can only use it one a target that isn't moving, but still. If Kurapika sets the condition to be something he knows the target won't do, it's just a killing ability.
And yeah, Dowsing Chain is an insane utility ability. Kurapika even used it to block bullets, for Christssakes.
And Stealth Dolphin is just broken. I know there's always the chance he'll get something like Leol's Big Wave and just die, but it's still crazy. Not only can you force someone into Zetsu, you gain their Hatsu. Not only do you gain their Hatsu, you can give their Hatsu to an ally. Not only can you give their Hatsu to an ally, but it works as a perfectly safe Nen baptism to non-Nen users.
It's just too much. Individually, I think these are all fine. Even if he just had 3 or so. But 6 abilities is too much.