Worth evolving?

Evolve that thing! If that's the best you can find in 125 candies, then it could be another 125 before you find something better, if even you do. A dragonite is still a dragonite either way, with or with out a couple of IV points

It depend on how bad you want that thing but if I were you I will wait.

IVs really don't matter all that much, especially when you're talking about pokemon that have very high base stats (e.g., Dragonite, Arcanine, Lapras, etc.). What I'd be more concerned about is your Dratini's level: I would evolve and power up a 60% IV level 25 Dratini before a 90% IV level 15 Dratini, no question, in order to limit the number of super rare Dratini candies needed.

FWIW, I have a 60% Dragonite with DB/DC; he's my highest CP mon and one of my best attackers. Not once have I regretted powering him up.