Latias ex was actually quite similar to Dragonite ex, as in it had to discard an Energy of two different types to deal reliable damage. There were definitely important differences, as Latias ex had lower HP but was a Basic, took Fire instead of Lightning Energy, and had different Resistances to work off of. Still, it was hard to make Latias ex work, just like other Pokemon that had to discard multiple types of Energy at once.
Latias ex had 90 HP, which wasn’t that great on a Pokemon-ex in most cases, but was fine on a Basic and didn’t have to worry about Desert Ruins. The Colorless Weakness was annoying, as Rayquaza ex could get two Prizes off if it very easily, and the occasional Crystal Shard was a problem as well. Luckily, Latias ex came with two fantastic Resistances: Psychic and Fighting. It not only took lessened damage from the many Fighting-types running around, but from the dangerous Gardevoir ex as well. Latias ex had a very average Retreat Cost of 2, and since discarding was not something Latias ex could handle easily, Switch was very useful.
Latias ex actually had a weak attack that cost 1 Colorless Energy, Hypnoblast, and it did 10 damage. If the coin flip was heads, the Defending Pokemon was put to Sleep. That was basically just a 25% chance to stop the opponent from attacking, so it wasn’t to be relied on.
The real attack to see here was Mist Ball. It cost 1 Fire, 1 Water, and 1 Colorless Energy and did an incredibly high 100 damage. Sadly, it was hard to use often, as it required a discard of 1 Fire and 1 Water Energy. There were ways to help this out, such as Swampert support, but having two different Energy types in the discarding portion of the attack hurt it immensely.
Latias ex was probably a bit better than Dragonite ex, due to the better Energy support with Blaziken as another option and the added Psychic Resistance. That being said, it still wasn’t good enough to use seriously. It might make for an interesting gimmick for a casual deck, but that was about all it could do. 100 damage was amazing, but the lack of consistency was awful.