Would you ever power this up?
Answers
And you hear wrong.
Species is more important than level and moveset. Level and moveset are both more important than IVs.
Within IVs, Attack is a little more important than defense, and both are a bit more important than stamina (HP).
A 15 attack may let you reach the last breakpoint at level 40 in a few very specific matchups. A 15 defense will save you a few hit points every single charged attack you take. The attack will let you do a few more points damage every fight, the defense will let you get off an extra charged attack once in a while. And at the higher levels, what we're focusing on here, a single HP or two will almost never make a difference. My best two Kyogres have 15/15/13 and 15/15/12 (ads), and I couldn't be happier with them.
So no, a 0 stamina and 0 defense are a deal breaker for me. Do a quick comparison, how many levels lower could a Dragonite be with 15/15/15 and have the same CP? Edit: I did the calculation. A level 40 Dragonite with 15/0/0 (ads) has a CP of 3320. A level 35 Dragonite with 15/15/15 at level 35 has a CP of 3325. So you're giving up 5 levels worth, and paying for a level 40 to get the performance of a level 35. This will cost you 88k dust and 118 candy, to match the perfect at level 35, and then your 15/0/0 Dragonite can't get any better (until the level cap is raised). Bad investment.
If you are in dire need of dragon counters (though you are about 2-4 months late on that one), then taking it to lv30 won't hurt too much. at worst it's 44k dust. I wouldn't ever take it above level 30 though.
I've got a bunch of piddling 70-87% iv dragonites at levels 31-34, which I slightly regret. Not for the dust spent, but now I don't have a lv 30 dragonite for any Lv30 max challenges. So I'd have to power another one up for that task. I'm never going to power these dragons any higher so they are kinda in no-mans land on the level scale.
Dragon. Probably not. I will admit to maxing a similar Machamp. I believe he has 2 and 3 for HP and Defense. I caught it at level 30 before I had any good ones or TMs were a thing. Rolled the right moves and never regretted it. I didn't max him right away but I'm working on a set of 12 champs(3 more to go). I often lead with meathead as the energy gain is noticeably better and the opponent may be less likely to rapid fire charge moves.