Heroic raids are designed to take 6+ months for most progression guilds to learn, but it seems like most guilds never finish before the next tier. On any server there seem to be at most 1-3 guilds that complete all the content. So there is a remainder of 5-7 heroic progression guilds on a 3day schedule that only get up to 12/14H before the end. So there seems to be a world of difference between guilds that down all the bosses in 2 months and farm the rest of the tier, and the guilds that grind ceaselessly for 6+ months, but somehow never get there.
Would it bother you to be in a progression guild that could not complete the content? Would you feel like you were missing out on meaningful content especially when the hardest/most interesting fights are at the end (H firefighter, HLK)?