Notice the trend of Pokemon that are Weak to Ice is what I'm starting with here. Half your Team is weak to Ice, so a Froslass of sorts or a Pokemon with an Ice Move can wreck havoc in this Team. Also, I see you are weak to Stealth Rock is spread all over the Team. Lets try and fix that here.
Xatu is one of those Pokemon that doesn't belong in UU, being too weak per say. If you decide to keep it, at least make this Xatu a Dual Screener, not something to damage Pokemon. It has Magic Bounce so it can't get Taunted, take abuse of that. The Dual Screener Moveset is:
Xatu (M) @ Light Clay
Trait: Magic Bounce
EVs: 252 HP / 252 Def / 4 Spd
Impish Nature (+Def, - SAtk)
- Light Screen
- Night Shade/Thunder Wave/U-turn
Your choice on the last Move depending on your liking. The Dual Screener variant will support your Team more in the long run then running Moves like Psyshock on it. This Xatu has to be used with great timing, otherwise it will fail.
Registeel was a good choice to put with Xatu. My one recommendation I really suggest is to replace Toxic with Thunder Wave. Thunder Wave not only makes your Togekiss more annoying, but it helps shut down fellow Scarf Users like Rotom-A, Chandelure, Darmanitan, and the rare Zapdos. I'm not sure on the Stealth Rock moveslot there due to having Xatu on the Team, but whatever. Also, complete the EV Spread by giving it 4 Def. As Trachy said, it might help you survive by 1 HP.
I had a major problem with Weavile on this Team. Sure, he is a great Physical Sweeper, but look at the weaknesses that Weavile is spreading on the Team. Fighting, Fire, Rock, Weak to Stealth Rock etc. This is only hindering your Team, making you more succeptable to things like Darmanitan, Mienshao, Scrafty, Rotom-H, Rhyperior etc. Replace him is all I would suggest here so this UU Team can kick ass. This opens an opportunity to use Swampert on the Team. You might be thinking that you already have an SR User, well Swampert won't be used for that at all. Swampert was in OU due to his massive bulk paired with phazing Moves and great defensive typing. So I suggest the tanking variant here:
Swampert (M) @ Leftovers
EVs: 252 HP / 252 Atk / 4 Def
Adamant Nature (+Atk, -SAtk)
- Toxic/Ice Punch
Here you go. Swampert gifts you with a reliable switch-in to Darmanitan, while phazing the Set-up Boosters like my variant of Scrafty(SubBulkUp). Swampert covers your Electric and Fire Weakness as well, while still having the same Physical category as Weavile, but with way better synergy Typing wise. Your choice on the last Move, due to having Toxic replaced on Registeel.
Rotom-H is solid, keep it like that.