Does IV make such a big difference?

After many research and thoughts on this topic, here's my conclusion:
Because of the rounding, IVs don't matter most of the time, but when they do, they matter a lot (a jump).

There is actually not much to do in this game. Collecting and searching for better duplicates of existing pokemon is the only real end game. So in that regard, IVs are all that matter even if they have little effect on combat.

Yes, like Deoxys. A 15 attack IV one deals 1500% more damage than a 0 ATK one.

IMO I would believe it does matter now - after the introduction of TM as we no longer need to worry about not getting optimal moveset after evolving.

If considering the IV effects in legendary raid I would think it should be less though - since anyway you require a minimum team of players to contribute.

But I would say IV becomes important when solo-ing tier 3 raid boss coz it all depends on your mons' dps and defensiveness/bulkiness. For non-legendary mon, I have set a minimum acceptable IV of 95.6 for investing dust/candy on it.

My lone Mewtwo is 10/12/13. I named him "Mr. Perfect". Sure it's a lie but it alleviates the OCD I sometimes get with IV's.
He's perfect and I'll hear no more about it.