What you are doing here is comparing a fight with no downtime to one with downtime and then making the logical connection that a flatter damage profile constitutes a nerf when there is high downtime. However while this is true it’s not the comparison being made. The comparison being made is between PCT as it’s designed right now and PCT if you moved muse potency to filler
Since you can use muses during downtime every muse you move into downtime gains you filler, if the filler is buffed at the expense of the muses you only gain because you gain filler by putting muses into downtime but you lose nothing to the lower muse potency because they were already being used in downtime
So if the filler was buffed at the expense of the muses the more downtime you have the stronger PCT gets relative to other classes because it’s uptime filler is relatively stronger than it is now but muse potency is still flat downtime gain because you aren’t “dropping filler” relative to the other classes if everyone is in downtime