Really the Zodiacs probably aren't all battle-centric hunters anyway are they? I mean, yeah all of them need a certain level of proficiency in fighting but surely they have other focuses which make them valuable and important hunters to the Association.
Also I wouldn't say the Chimera arc was a mistake. What does that even mean? For starters, it kept Togashi working. He must not have had many other ideas at the time to do it for so long. He may have quit without it. And also it was amazing story-telling. So many genre shifts and outrageous character development. It could have been much shorter but all-in-all was fantastically done.
I wouldn't say CA arc was a mistake but it seemed like a different series. It was completely unrelated to the protags goals. It was a way to make the manga returns to its origins IMO and Gon finally got a Hunter job.
I don't think the Zodiacs are weak. They are all good enough to be Netero's training partners. Hisoka rated them but we don't know on what. I assume it's their aura volume, of course he rated them all below him but he also said they are the only worthy of fighting him. And don't forget that their Hatsus are all unknown, Aura volume isn't the only criteria. To me, Togashi wanted to remind us that Hisoka is a beast to rate them like that and this arc made me reevaluate Illumi's character. I thought he was just afraid of Hisoka before.
I wanna see Feitans nen ability more!
I want to know how and why the Ant Queen come to Human World
It's so crazy how many amazing characters Togashi has to work with.
The how and why?? might be explained when we visit the dark continent, since perhaps there is a tilt in the food chain on the dark continent; therefore the queen decided to flee. Maybe the climate was too harsh as well.
I picture the dark continent as a place with volcanos, sand/thunder storms, dark smoke that covers the sky; or similar to the hellish places that were shown in yu yu hakusho.
It's more like Toriko's Gourmet World I would say. And there are even other human species.
We are talking about the level of the beasts but we are not even trying to speculate about "Armageddon". From what we know so, the whole world will be endangered.