There use to be quite a few good 16 man guilds out there, but the majority of them left the game due to the easiness of it. I imagine that a great amount of what is left of 16 man guild's rosters are players that would most likely be on a B team, and not a progression.
Speak for yourself. Our roster is nearly the same as before when we pulled out World Firsts. Granted, this time around we don't have the luxury of raiding on a weekend- one can still say that 16man is far more difficult than 8man. We are not a B team at all or close to it. Seeing guilds clear all the content in 8man while we're still putting in attempts on tanks just shows that 8man is definitely easier. Again, this is coming from a guild that had top progression in TFB. I am not saying 8man is extremely easy- only that it is undertuned. If you're only putting in 2-3 attempts per fight in order to do it on its hardest difficult- its undertuned.