Given that infinite Hail isn't going to exist in UU, wouldn't Walrein be using Thick Fat instead of Ice Body?
Also, it's worth noting that Draco Meteor from a neutral nature, 0 EV Flygon does 42.45% - 50.00% to a 252 hp Walrein, while a neutral nature, 252 sp atk Draco Meteor does 55.90% - 65.80% (assuming LO in both cases). Either way, Walrein doesn't have reliable recovery, so it can't switch in repeatedly.
Walrein definitely can't take repeated blows from Flygon especially considering that it takes 25% on the switch-in from stealth rock, which is quite abundant everywhere.
I suppose that means Specs Flygon can OHKO with draco meteor after stealth rock damage right? Just wondering.
Seems kind of odd that Flygon would be staying in against Walrein anyway since it risks getting an STAB ice beam in the face.
Also, about Shedinja moving down to UU, remember, the guy did get a lot better this generation, in fact quite a bit better. It can now basically have an extra life with focus sash, and with no weather in UU, the only way to kill it is by attacking or stealth rock. A lot of pokemon are in UU because of a harsh weakness to stealth rock, so most teams will have a spinner anyway, so shedinja just has to be worried about getting attacked or statused.
With swords dance and focus sash, shedinja is guaranteed to get a swords dance off and then it can really hurt things with shadow sneak.
Although, I don't actually mind if it does get moved down to UU. If it is moved down it will be a big threat there as teams will need to make sure they save something to kill the guy, or else he'll just come in late in the game, swords dance as much as he wants and then kill everything without them being able to do anything about it. Just my two cents on the ghostbug though.