Would you power up a D’Nite right now?

personally I wouldn't power up dragonites as they are generalists and the current meta is geared towards specialists

Depends.

You can't use your D'nite candy for the others. If you have a lot of dust, sure, power it up. If nothing else, it will make an effective DPS mon against the other dragons when they do come.

But if you're dust limited and already have a few, I'd hold off. Of course, if you don't have a Dnite already, then max it out.

I have two Dragonites powered up to 35 and 39 that I use to fill in raid teams if I don't have enough better counters. I rarely need more filler beyond them.

Yes, Dragonite is good at everything

Would you do anything with a third one right now? I also have 2 at level 40 and have not felt it necessary to add another maxed one to the roster. It is a great filler mon for raid teams and could be more worthwhile when Rayquaza raids come.

If you have one DT/O one and a DT/H one, I probably wouldn't. How often do you actually slot in more than one - usually meant to patch up a hole in a team of specialists or sweep a gym.