Well, the guys at Smogon tend to test everything before making any changes on tiers. Tests that usually take some months IIRC.
It would make sense for most people playing competitively to have them as their first source to check what to play, and what not to.
About breeding for perfect, I'm not so sure. It does take a lot of time, but since we now have Internet, and a way to clone Pok?mon... It's easier to get that near-perfect IV baby if many people try at once as a team, then clone the result and distribute.