As it turns out my characters was already tough enough to clear 2nd stage and 3 star it. My biggest mistake was putting down Heavy infantry instead of valkyries.

But Mages is so obscenely expensive to summon man. Difficult to hold off hordes of magical damage units that is mostly vulnerable to magical damage cuz of high prices on mages. 28 for valeria and 25 for vanilla mages. It'd make a world of difference if mages was 20 points.

So yeah, lvl 20-10 characters can 3* the 2nd stage if you're fast enough to click fast on korean starcraft levels of clicking hax speed.