Hunting Grounds
This got nerfed way too much. I think that there should be 2 Mastodons allowed per Hunting Ground, so Hunting Grounds would at least be useful in multiples. I'd be in favor of an even bigger change though.

Agitator
Back up to 1XXX, maybe even 2XXX. It's very strong.

Scry Pool
Down a domain level. It's worse than the Geographic Society.

Ronk's Factory
+1 Vision.

Loxlorn Sail
-1 flux. It's right on par with Longshadow Clock.

It should be noted that all of these buildings are very weak when compared to Astridian Forum. Even after the suggested changes the Forum brings a better bang for the buck than any of these buildings.

Prevailing Winds
I've been playing with this quite a bit (it's fun when combined with Planar Intersection, Air), and I think it could cost an extra flux, as it is surprisingly useful. Prevailing Winds can just shut down certain decks, especially if you have 2 or 3 out at a time.

Nightfall Bounty Hunter
Should be able to move through enemy Figures.

Greck
Give it back +1 Vision. Making the eggs swim stopped the worst of the shenanigans.

Mystic Feedback
This just isn't very good at 3 domain. It's pretty frustrating that if you play a deck without MF and you're worried about enchantments, that you have to plan on going to 3 domain. I'd really like for this to drop a domain and get rid of the dealing damage part.

Have you encountered a Greck with Foul Termite Swarm and Planar Rift? It's still quite frustrating.

Mystic Feedback is very good for any deck that gets to 3 domains (it's good to have more reasons to get a 3rd level, 2-domain decks have been quite prevalent in constructed) without MF or CI, and good for many decks that have those too. The damage dealing is cool, and it's nice to destroy opp's seedling for a Brimstone Powder effect for free! What troubles me is feedback will probably be nearly must-have for sylvan decks, making Restore Nature's completely obselete, since it's just simply worse. Of course it will be must-have for DL too, but that's ok because DL has to have some way to deal with enchantments and a DL spell for that wouldn't make sense.

Other comments I agree with mostly.

Hunting grounds: 4 mastodons for 1 HG would be fine. 2 is too risky, they all may be next to opponents base. And then you lose to your own enchancement what is not the intended behavior I think...

Greck: give back the 4 vision.
Hatching eggs now needs more set up, it is OK.