From my experience, Foveontosa works best with units that don't rely on its range boost to deal damage, but can benefit from additional range. In other words, don't put RNG 1 units in row 2 expecting Fov to always work since it's easy to get caught with your pants down.
If you want to achieve a similar effect to Shathia, I recommend Silverion (https://alteil-login.gamepotusa.com/cardDB/detail.php?id=909
) -- it takes a bit longer to get ridiculous damage, but it has a natural 2 RNG and grows each turn. Plus, Holy Ray with additional range is powerful. Shathia would be better as a front row unit.
In addition, I recommend adding in some tanky units. Beast Statue won't be able to engage all day.