There is absolutely no sense including 8-man raid groups in these progression charts. 8-man TFB and EC Nightmare are a joke to any serious progression based guild.
If the 8-man raid groups want to gloat about their progression let them do it in the RP forums...
Somebody's mad that the bads his guild has to carry to fulfill the epeen requirement is holding back progression. Having said that, I agree that 16's are more fun and have always been my guild's goal. Are they harder beyond getting the right personnel...no. You could make the argument that 8-Man's are harder because one mistake usually ends in a wipe while the bads you are carrying around are face first on the ground but the scaling from 8 to 16 accommodates that.
Btw, what Serious Progression has your Serious Progression based guild accomplished? Got past the medpac phase on T&Z yet? I kno that mechanic is much harder on 16 man.