Latias is my new favourite non-Uber. Unlike your standard Grass Arceus, Palkia, Gastrodon, Latias can check most variants of Kyogre while being immune to Spikes, which is everywhere in the metagame. Grass Arceus gets 2HKOed by Specs Kyogre after SR and a layer of Spikes, while Toxic Spikes completely ruins it. So far, 252 HP / 252 SpD Calm Latias is working just fine, able to take 2 Water Spouts from Modest ScarfOgre and Recover it off easily. It take about 40% from Scarf Palkia's Spacial Rend after a Calm Mind. Try it out, everyone.
After trying it out, it looks like it can check most kyogre forms but its weak to things like BU dialga and in particular toxic <.< (gravity just sucks D: if its used on it, then again I use gravity chansey so don't take my word), what poppycock and pocket said about it only makes it worse. Latias is also a bit weak physically being flat out 2hkoed by giraitna-o's shadow sneak, and ohkoed by a nonivested outrage from the same thing. I'd say it needs soul dew to do work but when I tested it levitate wasn't really helping much.
I still think it has a small niche though. IT CAN beat crogre in a cm war (assuming it has psyshock) and sweep or phaze while not worrying about switching in to deathly damage from spikes but i don't know if something else can do that better. Then again i only tested cm/recover/refresh or dragon pulse or psyshock or sub or roar /dragon pulse or psyshock with shrang's specially defensive ev spread. It's high base speed enables it to phaze before a lot of stuff with roar, and access to recover, refresh, sub, roar, with a dragon typing and lefties probably make it one of the fastest bulky phazers with a water, ground, and fire resist. Leftovers can make it usable over arceus who has to accept a sr weakness and horrible flying typing to gain a spike immunity.