Hmmm... you do have very valid points.

And Noel’s Strategist subclass/specialization seemed to come with skills that were tailor made to defeat such a foe, or was it vice versa?

If we take into account that Noel was manipulating things behind the scenes, it makes more sense. But you're right, it does feel like lazy writing.

In particular, I don’t recall the Link ability being revealed earlier, so it feels like a deus ex machina.

Oh yeah, I found that totally odd as well. They definitely didn't reveal it before. And they had supposedly been practicing a lot with it so it definitely felt like they pulled it out of nowhere. Definitely the worst part of the episode. I guess it didn't affect my judgement as much because I assumed Noel would pull something out of his butt anyway? He had already foreseen Blue Beyond winning the challenge.

Conversely, Leon’s supposed to be this amazing Talker, same class as Noel, and same B rank I think(?), so what was his subclass/specialization, what abilities came with that and why weren’t they useful?

Leon's a Knight or a Guardian or something, not a Talker. He's not the same class as Noel, but he is B rank. So all his attacks were telegraphed cuz mind-reading. Although, he does have that angel wings insta-cast thing that should have been useful but he doesn't use it? I don't think they gave a good explanation for that.

Heh, I just noticed that Leon and Noel are each other’s name spelled backwards.

And they're like, exact opposites! I hadn't noticed either! Huh, go figure.

Well, I almost totally gave up on this series a while back so maybe my expectations are low and I'm satisfied with this level of narrative :p