It's quite clear you haven't understood the class yet, so asking for changes based on your knowledge and observations doesn't make sense.
Take your time to level it to max level and play it, low level potencies and dps mean nothing because the leveling phase is a very short one in the grand scheme of things.
You made a lot of statements that are simply false or are ignoring something important.
Nobody transposes after Flare/ Despair because it would clip and you have Aspect Mastery to change to Umbral Ice 3 with Blizzard 3. Transpose is either a tool for downtimes/ between pulls (especially once you get Umbral Soul) or for highly optimized gameplay.
BLM has by far the lowest APM of all dps jobs because their dps comes solely from GCDs, they have no oGCD damage; they have oGCDs that enhance/ affect GCDs (like enforcing a proc) but no oGCD damage itself. Their primary cast is longer than the GCD by default. Which means their GCD spells have to have higher potency than e.g. the average NIN combo skill because the NIN also has TCJ, Ninjutsu, Raijus, Bunjin, Meisui etc. - all fairly weak individual hits but they come in addition to their GCD combo hits.
BLM also has absolutely no dps support, meaning only their own numbers count while every dps except MCH and SAM also has party buffs that are factored into their overall dps. The fact that BRD and DNC (and MCH, rip) are behind not just BLM but pretty much every dps has nothing to do with the number on their highest nuke and everything with the outdated concept of range tax.
Balance is fine for the upper half of the dps because they're extemely close to one another. The only thing that is not fine is that we have a noticable gap between the upper half (MNK, BLM, RPR, SAM, NIN, DRG) and lower half (RDM, SMN, all phys ranged). Within the hard hitting bracket BLM is balanced; not because of movement required to dodge mechanics - a good BLM can do that without ever dropping dps - but because their consistent damage evens out against more burst-y jobs like NIN and jobs that bring party buffs.
Yes, low level balance is scuffed. A DNC and RDM absolutely steamrolls dungeons, SGE and SCH regularily out-dps proper dps in big dungeon pulls etc.; potencies are adjusted for lv 90, not low level content because they factor in having access to the whole toolkit. Every few levels a different dps is completely op while another is falling behind because one got access to their cool shiny skill that signifcantly increases dps while the other got something "meh" that won't really work until higher levels.
Adjusting low level potencies in a way that affects max level balance is something that should never ever be done because it completely screws max level, the level where you'll spend the majority of your time on, and all max level content.