I don't have exact numbers on it, but it seems like IV's don't play *too* much of a role in the game. If you find a perfect moveset on a Pokemon with 50% IV's, it may very well be worth maxing out.
Right now I'm playing by the rule that 70% IV and perfect moveset is my minimum... but for example, I have a Snorlax at 55% IV's and perfect moveset, and a Dragonite at 55% IV and perfect moveset, and I'm not sure whether to upgrade them either.
Need more concrete information on defense, stamina, attack, CP, all that.
It is not worth upgrading anything with low CP right now, although it's worth keeping high IV Pokemon in case. They have just balanced moves, and it'll happen again most likely.
This post was edited by Canadian_Man on Aug 3 2016 02:18pm