I don't agree with this at all. The final episode made clear they why of Reva's arc. She's here so Obi-wan, and the audience, can hold up a mirror to Anakin and to reinforce that Vader isn't Obi-wan's fault.
The audience already knew Anakin's turn was not Obi-Wan's fault simply by watching the PT. There's not many characters in film with a larger "You asked for it" sign flashing on their forehead more than Anakin.
The series did not need Reva as a "mirror" to explain what was clear about Anakin in AOTC & ROTS.
Once again, Kenobi had Vader at his mercy, and just... let him walk.
Oh, that's supposed to be a form of the
"mercy" line he would later say to Reva. Really? Well, this series is nothing if not a pile of inconsistent character motivations and perceptions when compared to its "future"--the OT. In the OT, Obi-Wan was of a long-held view that Vader was
"Only a master of evil" and
"...more machine now than man. Twisted and evil", and Vader was certainly that in the post-ROTS decade, so he (and Yoda) were so sure Vader was the pure, irredeemable embodiment of evil, that their training of Luke was to defeat--not save Vader (who was perfectly content to get his own son to sell his soul until his last-minute act of self-interest).
Knowing what would happen as he did it- that Vader would go on to murder, destroy, oppress, over and over, and nobody else would be able to stop him.
Weakest point in the entire, badly written story.
Agreed. Anakin selling his soul to the dark side and his crimes up to the point of this episode was not Obi-Wan's fault, but the series painted him as uncharacteristically shortsighted to think Vader--a man Obi-Wan knows
lives for evil
and cannot be turned to the light (as he believes throughout the OT) should be left alive.
And apparently the Grand Inquisitor and the captain of the SD didn't put out any patrols to cover the back side of the planet, once again allowing the quarry to fly away free as a bird, so Vader could snarl to the emperor about how 'he won't evade me again!"

Uhh, sure he will. Just like he did the last time. And the time before.
Yep, and Vader and the not-so-grand Inquisitors would never have Obi-Wan's scent again--until the
Falcon just so happened to be captured by the Death Star.
This might have made a decent 2.5 hour movie, done properly As a six part miniseries as written, it just stank.
Indeed. It was yet another Disney-SW production telling a story that did not need unnecessary side plots and characters to explore Kenobi's trials in the decades before
Star Wars.
Oh, and the other bit of fanservice dialogue swiping: Luke saying
"I'm not afraid," as if that trait--which Luke expresses to Yoda in TESB--needed to be established in his childhood. At least write the same thing in another way. Sheesh.