So, my feedback on each of the "current issue"

Mana rework
I'm fine with it. We're suppose to do BlizzIV so wether it's a natural tick or a cast matters not.
It is killing the alternate rotation but that's clearly intended but I don't mind it. It probably was a balance nightmare, you design a job to be played a certain way and the optimal way is a clunky mess.
Sure, there's the appeal to the more HC players, but frankly I feel like it left the job in a weird spot.
Regarding low level before umbral soul is unlocked. We'll see what they plan for tomorrow, but the easiest fix would be to make all ice spell cost 0 mp.

Ice Paradox
I also wonder why it was removed.
It made sens thematically and gave us a bit of extra mobility.
However I remember seeing post of people complaining that Ice Paradox was annoying because it forced them to spend more time in umbral... My guess is that people will complain no matter what.

Fire Paradox
I actually like the change. Being able to have a garanteed instant during the fire phase is nice. Instead of doing 3P3 I simply do 4P2.
It also allows for some triple/swift cast weaving nicely.

Thunder
I like the change that we get one after each transition. Not being tied to a proc makes for a smoother experience.
However, the potency reworks makes it a bit weird to use and relay it to an umbral only cast (ideally to weave transpose).
On one hand it's fine because we were already doing that, thunder in umbral. On the other hand it makes it a very poor movement tool.
Perhaps dropping the duration to 15s (while doubling the DoT potency) would make it better as we'd have to use it twice as often. It would also make us not waste half our procs.

I do not believe the nerf to double dot on 2 target is a problem. There aren't that many situations where 2 high hp target are present and tbh with the proc being available at every stance swap, double doting isn't that hard.
Garanteed Thunder proc for 99% of our single target dps compensates for that 1% of the time there are 2 targets. It will still be fine as we have 2 thunder per full cycle, we'll just not be able to have perfect uptime on 2 targets.

Flare Star
Here is where I think something's gone wrong.
As mentioned many times, the new Flare Star works as a finisher which requires a full fire phase to be used.
Which is a twofold problem.
1- We already have a finish in single target and that is Despair. Having an extra finisher every cycle makes the spell redundant
2- It requiring 6 FireIV makes it so that closing an astral phase early, for whatever reason, is not only a DPS loss but a frustrating experience. You're at the 5th FireIV and the boss is about to transition? Enjoy your loss.

The stack not being held in umbral phase obviously is a big reason why problem 2 occurs.
The spell is however very fun in AoE.

Imo, a simple solution which would make the whole experience better would be to make Flare Star stack only obtainable through Paradox, Despair, Flare (x3), use of manafication (30s buff granting 1 free cast)

It would address problem 1 as it would stop being a finisher. You wouldn't always do it at the end, you would just do it after 3 complete phase.
It could be after the third despair or at the beggining of the next firephase.
As an additional benefit, the spell would feel more special. It is something you'd be building over 3 cycles, therefor very high potency could be attached to it.
Its long cast time would also reinforce the whole "big boom incoming, finally!!!"

The second problem would be adressed by not tying it to FireIV but Paradox and Despair which would bring back flexibility regarding shortened fire phase. With only 2 casts required per FirePhase to build the stacks, beside 3s firephase (FireIII > Despair), we'd always be able to get our stacks.

Obviously, this would require the Astral Fire stack to be held while in Umbral Ice. Additionnally, because of the long windup, the stack should also be kept without Enochian to prevent frustration during 1min transition in some savage / ultimates.

Flare dmg
No one talks about this one but, could Flare simply becomes a flat damage on all target? It is already annoying enough to swap target on a 4s cast in dungeon, but on top of it since there's drop on additional targets, we can't simply spam the one target in the middle of the pack as it'll die before everything else.
BLM AOE doesn't seem to be stellar atm so that could also serve as a small dungeon buff.


Summary
Overall it's fine
Waiting to see the changes, but an easy change regarding mp would be to make ice spell free
Thunder would probably feel better with a bigger impact or shorter duration
Flare Star is atm redundant and would, probably, feel better if reworked as a rarer yet much harder hitting spell by gaining charges through Paradox/Despair.
This would also fix the "short fire phase" issue BLM currently face.