A few things here

PCT needs a nerf but it needs to be a specifically targeted nerf and unfortunately it won’t fix every problem

At its core PCT is a class functionally designed to destroy ultimates, there is no way to balance PCT in ultimates without fundamentally changing its design and completely ruining its flow in other content. The common suggestion of “only let it cast muses in uptime” simply does not work and would be a far worse balancing problem than currently because instead of being able to turn downtime into uptime it now has to turn prior phase uptime into downtime which is a far worse balance problem. Removing this quirk is also something that reduces the design of the best received class since 4.0

Now as for the actual nature of the nerf there is quite a few considerations you have to put into it. Here are a few

1) moving potency from the muses to the filler is a buff not a nerf in ultimates
2) removing the raid buff element of starry muse makes starry a dead button between level 70 and 92
3) the hammer combo is only a very slight PPS gain over filler so can’t be nerfed far
4) without mog/madeen creature is only a very slight gain

So the nerf would either have to slightly nerf the filler combo or nerf the items you stick inside the starry muse window (say nerfing star prism and rainbow drip). However buff feeding means that there will always be an element of PCT that dominates over the very static BLM

also of relevance is that pointing to ultimate is not always the best idea, of the current clears both SCH and AST as well as DRK are near as ubiquitous as PCT, top end players simply lean on a meta that tends to permeate the entire top end even if the differences aren’t as large as implied