Latias @ Soul Dew
EVs: 112 HP / 204 SAtk / 192 Spd
Timid Nature (+Spd, -Atk)
- Dragon Pulse
- Hidden Power [Fire] / Grass Knot / Thunder
- Roar / Refresh / Toxic
This is a support Latias set I have been running and really enjoying. The EVs come from the DPP support set and ensure that Latias outspeeds Garchomp when it's not Choice Scarfed, survives two Water Spouts from Choice Specs Kyogre and is able to 2HKO support Groudon with Dragon Pulse. Adding more Speed EVs to ensure outspeeding Terrakion is definitely an option, but in my opinion not worth it on a support set, seeing as Terrakion is less problematic for it as for a Calm Mind set for example. Hidden Power [Fire] is amazing for nailing Forretress and Ferrothorn, who both like to come in against Latias to start laying down their entry hazards. I personally run Hidden Power [Fire] now and I've never looked back. This doesn't mean, however, that Grass Knot, Psyshock and Thunder aren't perfectly fine options for a secondary attacking option.
For the final slot I recommend either Roar or Refresh. Roar works amazingly in this entry hazard dominated metagame, especially seeing as Latias can easily force switches to rack up the damage done by Stealth Rock and Spikes. It's also very helpful against several Calm Mind Pokemon, who otherwise could be problematic to deal with. Examples are: Kyogre, Arceus-Fighting, Arceus-Grass and Manaphy. Refresh cures the ever dreaded poison which can be caused by users of the move Toxic, such as: Lugia, Ferrothorn, Forretress, Chansey/Blissey, Cresselia, Gastrodon, Gliscor and Heatran. It's also very helpful for when Latias gets paralyzed by Kyogre's Thunder and perhaps even when Chansey/Blissey uses Gravity in combination with Toxic Spikes, although this is very rare.
In conclusion I want to give Wish a mention, seeing as Latias is one of very few Pokemon viable in this metagame that actually has access to Wish (Alongside Chansey, Blissey and Jirachi). A Dragon Pulse - Wish - Protect/Recover - Thunder/Psyshock/Grass Knot/Toxic set could work for sure, I personally believe that after Wish got a mechanic change ever since Black & White were first introduced, this job is better left to Chansey or Blissey.
I encourage you all to try this Latias set out, I think it balances support and offense just about right, which in my opinion, is what Latias should do.
I don't know if support is the right word, that Latias doesn't support the team at all unless its spreading paralysis or poison (I AM NOT SURE IF ABSORBING SPECS SPOUTS IS SUPPORT, IF IT IS SCARF PALKIA IS AN EXCELLENT SUPPORTER, AND IGNORE THIS SENTENCE), and even THATS a stretch -_- (thunder and Toxic are slashed). Honestly that Latias looks like its standing there, waiting for something to happen. It could easily be turned into set-up fodder if its running refresh, since it can't exactly status or phaze stuff thats trying to set-up, like Extremekiller, or even worse, variants of Calm Mind Arceus. If its not running Refresh it becomes toxic bait, and unlike either of the CM sets, it can't boast a threat to Blissey or Chansey meaning they can just stroll in on any of its weak moves and Toxic it. Unboosted Dragon Pulse, while not exactly weak, is far from strong. It barely 2HKOes no investment Extremekiller (42.52% - 50.39%), while failing to 2HKO stuff with even a little bit more bulk, like Support Dialga. Regardless of the case Ferrothorn still can waltz around Latias, setting up spikes everywhere as Hidden Power Fire will tickle in the rain, leech seed and protect will allow it to easily handle Latias and it can Gyro Ball for the 2HKO whenever needed. While the other two sets have the same ferrothorn problem, the stall breaker can at least try to bounce around it via substitute or roar, potentailly setting up on Ferrothorn using Power Whip (Substitue may even help pp stall Gyro Ball Ferrothorn). While the offensive pivot spread doesn't have a way around Ferrothorn, it can at least hurt steels via +1 Thunder and take out Chansey and Blissey with Psyshock (granted Roar can do something a tad bit similar...)
I think you tried to combine both sets and ended up creating a set based around Latias trying to support. It sadly can't do that unless its running Dual Screens, and it actually is a bit inferior to Latios at that role due to memento (I'll put a dual screen set in OP if it gets enough support, since refreshing an Arceus with Healing Wish CAN be cool I guess...)