That's the Spirit
While the scene between Korra and Zaheer was fantastic, getting to that was the low point of the episode. The spirit vines in Republic City are grabbing people, starting with Ryu's tour group (the airbender voiced by Jon Heder is apparently rather ineffective as a bender), and later Jinora. The vines seem to be reacting to the Earth Empire harvesting the banyon-grove tree back in the swamp. For some reason, those captured by the vines are placed into weird plant-pods while their spirits are locked in the spirit world.
At its core, it's not a bad story, and it works to connect other elements on the episode. The problem is that it takes a while before the story becomes interesting (Korra heading to Zaheer) and the purpose behind the pods is never given. This might be a question that is answered later, but as far as this episode goes, the entire spirit vine plot just drags everything out.
- Varrick & Asami: There's some animosity between these two, but after Varrick returns with news of Kuvira's super weapon ("It's a weapon, but super!"), President Raiko teams up the two of them to engineer a solution.
- World Leaders: In the face of Kuvira's growing forces and news of her spirit vine weapon, Raiko wants to launch a preemptive strike. The Air Nation doesn't go to war, and Fire Lord Izumi understandably doesn't want to take her nation into battle, but she does agree to help Raiko defend their borders. Also, their lack of confidence in Korra's abilities is just another thing that ends up motivating her to seek out Zaheer
- Opal & Bolin: Bolin is quickly forgiven by his friends, but Opal's entire family has been imprisoned by his old boss, Kuvira. She lashes out at him viciously at one point and it would almost be too intense until her "apology" to Pabu for her outburst.
Bolin does get a little mature long enough to admit he should leave Opal alone, but at that point Opal recruits him for her mission (with Lin Beifong) to rescue their family. It's not clear if Opal's request was poorly written or if she's playing with Bolin's feelings, but either way he's naïve enough to go for it.
We're coming up on the end, and next week's episode includes a "surprise" we all saw coming (obviously, spoilers for next week in that link). It appears that Korra is fully recovered, but we'll see if there's still anything inside of her to provide a challenge in the coming battles. "Beyond the Wilds" also gives a great farewell to Zaheer, Korra's last surviving major antagonist, besides Kuvira.
Bottom line: The Zaheer portion is brilliant, and the rest of the featured characters are fantastic. The hostile spirit vines story takes up too much space to have no greater significance, though.
Recommendation: An old villain returns. Come on, you have to watch this one. Anyway, it's likely that this and every episode to the end of the series will be required viewing for those still on board.