The Paralogues I've experienced so far (Kana, Nina, Velouria, Forrest, Siegbert, Dwyer, and Sophie) aren't even that hard, although I did struggle a bit with Velouria and Siegbert. But the general consensus is to get the kids who have harder Paralogues (Ignatius, Shiro, Selkie to name a few) early so their Paralogues won't wreck your units.