These are all wrong, but the third one is super wrong. Clipping your gcd is a minor loss (in fact, if you clip for a Triple and get a Despair and Flare Star under it, it's a gain, if you only get one, it's pps neutral). BLM having "healer casts" with recast being longer than cast doesn't help that much in mobility beyond letting you slide cast more easily and without a loss.
The real problem with BLM is that your so called "mobility tools" are also your burst tools. So, each time you blow a Xeno or a Triple outside of burst in a way where you won't have that charge for burst, you lost burst damage. In a vacuum, this isn't a problem- it becomes a problem because of the strictly enforced 2-min meta nonsense and the multiplicative nature of raid buffs.
I have no clue where you got this idea that "no weave slots" are a "big obstacle to BLM mobility".
rewd already corrected you on your take that RDM is more mobile than PCT in general anyway. It's definitely more mobile than RDM, but PCT definitely hurts a bit when you need to to stop-run-stop-run nonsense for 12 seconds or something (Honey B. classic). Holy in White need to be build anyway. But you're correct in saying that Smudge is very powerful. I've stated it somewhere else, but smudge should be the standard for caster mobility tools. They should make AM work like Smudge asap.
You need to balance around a realistic performance in a generic setting. You can't look at top players in top groups, where they have a set kill time, voice comms, high level of performance and optimized strats and then balance around that. You also can't balance around people who can't even keep their gcds rolling.
Jobs, ultimately, need to be balanced around their most common use- df, pf and midcore groups. Because that's 90% of players. That's why looking at the top 5% logs for balance is a mistake, why looking at the max log is a terrible mistake, and why you shouldn't also care too much about what a player that only does msq and has a cpm of 15 does either.
A lot of people look at the 99% percentile and fail to understand that for 199/200 people you meet on the pf or df, balance for that level of play is meaningless. You cannot extrapolate that circumstance for most parties/kills. Or, at the very last, you shouldn't.
You can (and should) make the same argument about casters, because TOP p1/p6, SC1, and many other examples are absolutely horrible for casters exist right now. Or, honestly, let SE go wild and if you run 2x casters or 2x melee, the second of that subrole incurs a small penalty by dropping a gcd here and there (both HW and SB had examples of this and nobody died over it). Either way, the fight design isn't why you don't see 2x physical ranged- it's purely a damage differential because the role is underpowered at the moment due to bad balancing (well... so is the caster role, actually, which is why you also don't see much double caster at all).
This topic isn't even about Pictomancer, why the heck are we discussing it here? This job lives rent-free in most people's heads.
For Ramiee: I think enforcing double melee is crap, best meta was SB where you could do double caster and double melee, I wish SE added some manner of physical range synergy (like, some manner of buff that BRD or DNC gave to MCH that made it pop off) after rebalancing the roles a bit so double phys range was also a thing. Basically, the reason why double caster worked in late SB was because SMN+BLM had insane synergy. I still think we need a ranged-tax, but I also think the rdps between double caster/double melee compared to this hypothetical double phys ranged shouldn't be more than 2/3%, making it only slightly weaker.
But SE has no idea what they're doing with jobs soooo :>