All of the enemies are weak to strike, but magic still works quite well. They also have an element eater towards an element they are good against, which means a lot of Water eaters since the most common element here is Lightning.
It's a lot more manageable if you have a physical tank with good resists, as long as it's not Tidus, then use defensive gears/VC like Realm Reaver, Odin.
After a few turns, 3 more enemies Lightning enemies will show up as reinforcements.