I believe its intentional and they plan to account for this in terms of overall tunning.
One of the complaints that happened during Dragonflight in regards to tunning is some classes would lose a lot of single target to spec in AOE or lose a lot of AOE to spec in single target.
Doing this would allow the difference between going full ST or full AOE to be smaller as long as you account in how you balance the specs.
Now, they could make Rain of Fire, Implosion, Seed of Corruption baseline, and there is an argument for that.
There is argument to make a lot of talents baseline as many of them existed as baseline before Dragonflight or fill an objective who essentially is a core aspect of the spec nowadays.
Honestly, this is a direction who came with Dragonflight baseline stuff/required stuff became talents (Tyrant,Dreadstalkers, Havoc, Chaos Bolt, Rain of Fire, Implosion, Seed of corruption)
But hear me out, i don’t think it changes much as its in the 2nd of talents (you must pick Rain of Fire as much as you must pick Backdraft, or Demonology must pick Dreadstalkers or Affliction pick Writhe in agony)
they made Chaos bolt baseline in TWW and now Conflag is Talent 1(Who is another spell who is required and have ground to argue could be baseline) and you kind of picks either ROF or Havoc/Mayhem (who also could have an argument to be baseline) to progress
Now, they could make make Rain of Fire baseline, but here is the thing, i don’t think there are nice solutions to it.
Yes, people will say “Break Inferno/Cata and put Cata in there so we can acess both” but that is an illusion, it as much likely to happen as the removal of all the 2talent points while not filling the tree with new fodder nodes like the brickening did (leaving you with 39 nodes while picking 30 of them) i doubt they want to give both Inferno and Cata at the same time.
I can see them bricking Chaos Bolt back to the tree, in case probably some people will be satisfied as “chaos bolt you use everywhere, Rain of Fire you don’t” but point investment wise it ends as the same thing.
I can see it becoming just “Improved Rain of Fire” or “Talent who is mostly AOE” and just being a less impactfull progression than just Rain of Fire (As we must remember, they also use Talent Trees as a level up progression system).
And best, or worse case depending on point of view, a good, must pick, talent who is always good in single target and aoe who you are balanced around.