Sure thing, but assuming the players are adequately skilled (such is expected of the top-tier players anyways), the only change in those sorts of numbers in the vast majority of cases is a gear-check. Which means if the gear those guilds have already farmed from the previous tier isn't enough, then the barrier to entry is simply a time-gate of farming the bosses available to them in the new tier and getting that gear to further push their throughput. The skill barrier has the intended effect on lower-tier players, sure, but that's about it.

