Didn't try Ur-Child yet, but I did do some other challenges:
Anomalocaris is a jerk. It has a huge HP pool, and both of its attacks are a pain to deal with. Snaring Tentacle drains quite a lot of TP, which already isn't plentiful on any of my Protectors, but the worst is Greed, which somehow always scores at least one kill, meaning for most of the fight I'm wasting time trying to revive the victims. Ultimately, I had to eat the Instant Death Resistance dish, which made it much more manageable.
Yeah, uh, let's never do that again.
Solo Master Bird took a lot of tries. Firstly while he's not too dangerous with a full party, most of his attacks being single-target, he becomes much more difficult solo, as these single-target attacks hurt pretty bad, even for a Protector.
I firstly had to add a High Regen Grimoire, which while active, works wonderfully well with Healing Rhythm to tank all of his single-target hits. Chi Burst is annoying with the Paralysis, but ultimately it rarely lasts more than a turn, so it's not too big of a factor. Dread Stare's Fear is more troublesome, but fortunately he doesn't use it frequentely until later in the fight. Phoenix Strike does about the same damage as Chi Burst, but without any side-effects, so it's pretty much a free turn.
The biggest issue I had against him was trying to survive Crimson Cyclone. The first attempt with Fire Mist + Defend was good for up to 2 turns, but not three continuous uses. Another attempt with Protection Vow on top similarly ended in failure, as the toughest hurdle was when his health is in the red, where he pretty much spams Crimson Cyclone between Chi Burst and Dread Stare, which leaves me no room to breathe for both attacking him and healing myself, and it takes only for Paralysis/Fear to kick in and I'd be screwed.
Ultimately I had to resign myself to equipping the Dragon Orb, which turns Crimson Cyclone into free turns. With that, High Regen, Shield Rush, and Healing Rhythm, the fight became a breeze. A long breeze, but a breeze nevertheless.
Let's never do that again (bis).
For all the fear it inspires, the Shiny Dinogator took surprisingly few tries. During the first attempt the fight went actually pretty smoothly, as my party could survive Playful Bite two times in a row, and I never risked binding it for it to trigger Frolic. It was basically pretty smooth up until it hit around 1/3 of its HP, at which Pout promptly destroyed my party, killing two of my frontline Protectors. I still managed to revive them and get my party more or less in shape, but it meant I wasted several turns and Perfect Defense, during which it only became stronger ('cuz it was Shiny, hah), and I failed to kill it before I ran out of Perfect Defenses to ward off Pout.
During the second attempt, I kept a closer eye on its HP bar, and luckily used the first Perfect Defense exactly when it first started using Pout. I wasted the second one to a Frolic, which miraculously didn't bind most of my party's arms, meaning I could keep attacking it and using Shild skills. For the rest of the fight I used the three remaining Perfect Defense every two turns, betting on the hope that it wouldn't use Pout twice in a row, and that most of my party would survive it once. Ultimately, I managed to fell it on my second try, just as I used the last Perfect Defense.