What to keep? (general IV/moveset q&a)

I keep pokemons with either IV 88.9%+ or (84.4%+ & ATK 15).

I'd keep at least 1 or 2 of the final stage of all pokemon even those that are considered weak as long as they have 88.9%+ and have the best move set. Best moveset could either be defensive or offensive depending on the species (i.e. Arbok is offense oriented more than it is defensive).

As the CP update would prove, nothing is permanent and those weak pokemon might become monsters in the future. In my case, I kept an Alakazam, Rhydon and few Gengars before the CP change...and look where they are now.

One other thing that may happen in the future is breeding. We might have use for those weak pokemon (but with high IV) as breeding partners.

For highly rated pokemon, I'd keep 80+% espcially if they have high CP. You can always benefit from having 1 more hydropump vaporeon with 2k+ CP.

For rare pokemon, I'd keep them all even if IV's are low. You can always trade them whenever the trading feature becomes available.

Hope this helps

Unless it's rare or 100 I transfer. Easier just to keep the highest cp of each species. It's not like im ever going to use a starmie or vileplume anyway. Definitely not going to invest dust.

I hold onto too many Pokémon, I'm starting to weed them out using them in gym battles and transferring. What the hell am I ever going to use a 1935 CP, 89 IV Vileplume with Razor Leaf/Moonblast for? A 1247 Tangela or 859 CP Ivysaur on the other hand can have major value as a gym trainer.

Just depends, I'll keep 80+ IV Pokémon with ideal movesets even if I don't really use them, there can be moments when they are useful for training a gym.

To me it seems that nothing stays in gyms for very long. I don't think IV or move set changes that. In attacking gyms, I have noticed that move sets make a big difference in how quick and easy it is. IV seems to make a full pump or two's difference in the maximum CP of the pokie. Conversely, there seems to be very little practical advantage to pumping your pokie past level 30, or so. The pump increment gets halved, and the CP multiplier levels out. So, it gets very expensive in dust and candy to pump past that level, for very marginal benefit. If your embarrassed by your perfect move set but not stellar IV pokie's CP at level 30, you could probably just pony up the candy and dust to give him two or three more pumps, and he'd look just handsome for his brief stay in a gym. For attackers, if you take advantage of the type system, something with a 2K+ CP and decent move set will tromp anything that is weak against it.
One more thing to consider is that for a pokie with 2 or three fast moves and two or three charge moves, you should expect to catch or evolve a bunch before you hit on the perfect move set, and catching a bunch of high level perfect pokies, or their precursors isn't easy.
Anyway, in case it is not clear, I would nuture the pokies with good move sets over the ones with perfect IV. You may catch something later that is an improvement in IV, at which point you'll have to decide if it is worth the resources to achieve perfection. Personally, I'll focus on improving the high level pokies I have that still have poor move sets.