I fundamentally disagree that you have to balance around what people actually do without considering the high end at all.

If you were to, say, buff PCT's mobility right now because the majority of players struggle with using that mobility, then it would become insanely overpowered at the highest level. People already agree that it is definitely the strongest caster in the game, and in contention for the strongest job in the game. You simply cannot ignore the tools in the job when discussing how to design it.

Picto is absolutely inundated with mobility skills. Holy can be stockpiled at only a small DPS loss, the aforementioned hammer motif mobility combo is incredibly strong (without costing potential DPS the way RDM or BLM using melee combo/triple cast for mobility can), Smudge can be weaved after any casted GCD with either no uptime drop even on the CYM combo, and Comet, Prism, and the burst Hammer combo keep it moving even during 2 minutes.

Your suggestion indicates that for most players, this is not enough and PCT needs even more mobility skills, or perhaps damage buffs to make up for having "low mobility" (which is not true). But that would absolutely destroy raiding balance in perpetuity. The casual player base and hardcore player base exist at the same time, and there's nothing we can do to change that but acknowledge the facts. And, factually, PCT has more mobility skills than its caster kin (with the exception of the obvious Summoner).