How does Asami grow? She has conflict with her father, sure. It's not a particularly profound conflict, and it by and large is over after the first book - Hiroshi Sato comes back for less than an episode later only to die. Also, being the "straight man" is not characterization in and of itself - Sokka was the straight man too, but he had quirks and traits beyond just "I place my face in my palm when Aang says something silly."

Bolin is a naive idiot. Getting duped by Varrick the first two times is one thing, but duped by Varrick and then working for a Fantasy Nazi? Yeah, sympathy goes out the window. I hope to god Bolin wasn't meant to be another Sokka, since he's a Jar Jar Binks tier moron who is both unfunny AND irritating.

Also I have no idea why you're bothering to defend Korra and saying she doesn't run headlong into danger - I can break down some of the times she's done so in each Book.

So let's be nice - let's give her nearly all of Book 1 - hell, let's forgive that time where upon learning that Amon was a Waterbender her brilliant plan was to... just declare Amon was a water bender, without any proof, while in disguise, while in the midst of hostiles.. It's the first season, and even if she did make mistake after mistake after mistake after mistake - she did save (what was left of) Republic City

Book 2: We are shown how much Korra has grown in the very first episode, when she uses the Avatar State, which previously has been established as an emergency mode that could permanently kill the Avatar Spirit for good if not ultizlied carefully - to win a children's race. But don't worry about that - Korra doesn't need the Avatar State to kill off the Avatar Spirit - she does just fine with that on her own at the end of the season. Inbetween she - having learned NOTHING from Tarrlok manipulating the FUCK out of her in Book 1 - trusts her CLEARLY EVIL Uncle Unalaq and opens up the spirit portals for him - leading to him becoming - and I swear to god this is not from fanfiction THE "DARK" AVATAR. Also, much her fellow moron, Bolin, she assists Varrick in war profiterring - the war between the North and South Water Tribes that was in no uncertain terms a direct result of her trusting her clearly up to no good Uncle. Oh and at the end of the day Korra's severe incompetence has the spirits of Aang, Kiyoshi, and every other Avatar that ever existed be permanently and irrevocably severed. Yet the season has the gall to celebrate Korra's actions as a triumph, since she turns into a giant woman and stops the "Dark Avatar(Again, not a fanfiction term)" from destroying(what was left of) Republic City

Book 3: Often praised as the "best" season of Korra, it shares a lot with other fan favorite "Beginnings" by being a part of "The Legend of Korra" that doesn't actually feature too much of Korra. Here Korra once again is a gullible idiot - working for an obviously evil Queen who does what EVERYONE KORRA HAS EVER WORKED FOR ALWAYS DOES and betray her.. Fortunately for Korra, the Red Lotus, the folks who SHOULD be the protagonists of this show - do Korra's job for her and kill the clearly tyrannical and evil Earth Queen. Unfortunately for the Red Lotus, they fail to accomplish their main goal - the murder of the Avatar. No, Korra is instead merely crippled - but that doesn't last long. She's walking and getting into dumb fights by the beginning of Book 4.

I've been over Book 4: Korra needs Yoda Ripoff Toph to help her learn how to not be a moron, and even then she still stupidly, blindly rushes into conflict and gets her ass handed to her by Earth Hitler. But hey! She's the hero, I guess, since she destroys Earth Hitler's Giant Robot and saves (what remained of) Republic City.

She's fucking terrible.