Probably true, and overkill is a legitimate concern. That said, the updated pvpoke.com lists the best moveset for Dragonite in the ML as DB/DC/Draco Meteor. They base this off of simulations, not from pure math, so things like attack speed do matter.
The reason that DM is better than outrage is that you have Dragon Claw available. Most of the time, you’ll use DC, and do great damage very quickly. Then your foe puts in something that resists Dragon, and you need to hit it hard. Switching is a good option, but you can’t switch again for a minute, and if Dragonite is your last pokemon, it’s not an option. So instead of the wet noodle slaps DC would apply, you toss off a few more DB, and then hit it with the strongest PvP attack in the game, hoping you can do enough to take it out.
Hurricane is viable here too, esp. since it gets STAB, but the first round of simulations make it look like DM is the second move of choice. We’ll see if it stays that way.