He is right you know, average of a tier should be ~6 months max.
BRF came too soon, and HFC came too soon after that, BRF should have come at least a month or two after, with that logic, along with HFC, 6 months after that.
Problem is not what the top guilds do, but generally the general "Acceptance" of tiers seems to be somewhere between 5-6 months from all the thousand of posts about it the last few years.
If they released content with how the top 10 guilds do it, (Ignoring Emerald Nightmare, things are different) they should release a raid every 2 months, which is not possible unless you want rehashed models with 2 abilities.
I think even the worst raider can clear normal in a span of 6 months T_T