Ill post my reasoning as well since it's a WALL OF TEXT.
My involvment with the Latias test started from the beginning. I watched how people wanted to fortify themselves from most Latias sets and decided from then that I should make my first team as a anti-metagame team. However I decided that I was to test the waters with all the Latias and see how one of my current teams fared ,that I used on the Standard ladder. The team had no changes made to it from the Standard latter and it still won the majority of the battles against Latias.
I gained valuable information on what sets seemed prominent and began constructing my first team. The various abundance of T-Tars lead me to add Breloom to my team which is a fantastic switch in and allowed me to set up easily. The Latias set I used on my team was Specs Latias since its the only one who has a shot at taking down most T-Tar with Modest Specs Surf. The team ended up being Bronzong(Lead SR), Vaporeon(Wish Protect), T-Tar(CB Sp Def Heavy), Latias(Specs), Lucario(SD LO Jolly), and Breloom(Sub Seed). The team seems very standard with Specs Latias being replaceable with Specs Salamence barring SR weak but Intimidate ability. Overall the changes made to it were none as soon as it reached these sets. I won most of the battles with this team as I used it for a week and half.
However I began to see Stall teams featuring Latias and decided that I should aim for that next team next. I took some days off so I was not every day Laddering but changes were few and began to construct a Stall team with Latias being a nice bulky Screener with recover. At first it only for maybe one screen off since the Ladder was so T-Tar heavy so Reflect and switch as it pursuited for less than 50%. The screen Latias however became set up bait so I switched it to a Bulky Calm Mind Latias with Refresh for Status mimicking the Uber Latias. Over all it still managed to get countered by T-Tar, Scizor, Jirachi, and other Steels. My second Latias team ended up being Forretress(Lead 3 Entry Hazard Spinner Shed Shell), Blissey(Seismic Toss Wisher), Rotom(Sleep Talker), Shaymin(Sub Seed), Latias(Bulky CM), and Slowbro(T-Waver Fight resist). Shed Shell is bolded as an Item for Forry since Magnezone ran rampant and my team really depended on entry hazzards. This team managed to hold its own against offensive and stall teams but steels still managed to take down Latias. Both Team were used every time I was on Shoddy trying both out and also still used my Standard Ladder team from time to time and no changes were made then. I continued Laddering till the second to last day the test ended.
I managed to still use my Standard Ladder team to ladder and managed to make two Latias teams with different playstyles a Offensive Latias team and a Stall Team Latias team.
Now for the characteristic of Latias after battling with it and against it I have watched as it managed to sweep as CM but I also watched it fail against the abundant T-Tar. Overall its will be reviewed with the three characteristics in mind.
A Pokémon is uber if, in common battle conditions, it is capable of sweeping through a significant portion of teams in the metagame with little effort.
~Overall with the abundance of T-Tar and Steels like Jirachi Metagross and Scizor to name a few Latias won't sweep unless those pokemon are taken out. Magnezone gained rise in usage to accomplish this for Latias as people wanted to sweep with her. Overall she won't sweep unless your team is heavy stall or any possible checks or counters are taken out, a suituation in which most pokemon like Lucario can accomplish if they have the same support. In the end she ends up in the same boat as like Lucario and Salamence to name the popular sweepers.
A Pokémon is uber if, in common battle conditions, it is able to wall and stall out a significant portion of the metagame.
~Overall Latias in Suspect Ladder would have a hard time walling due to being T-Tar bait and various Steels. Defensively she can set both screens up, recover up, and either mono attack or Status with T-Wave. However Dual Screening can be done by other pokemon who can help set up with other moves like Memento Uxie and Dual Screen Bronzong. Overall her defensive capabilities are there but again other pokemon can do the same.
A Pokémon is uber if, in common battle conditions, it can consistently set up a situation in which it makes it substantially easier for other pokemon to sweep.
~Support wise she can maybe run some surprise set but I can't see her running like a good support set since those are few in examples. I myself can't seem to fully picture a good supporter that is not part of a Baton Pass chain or with a Trapping ability. I hope more examples are produced with this characteristic since it seems to be the lesser seen characteristic.
Overall Latias to me is OU.