They are heroes that are effective against myth units. But as Loki you get the random myth unit spawns when you mass them. They work great against myth units so having a few in your ranks is excellent.
As Odin and Thor you wouldn't make as many as when you are Loki because Loki has faster and better Hesirs.
"To love Christ -means not to be a hireling, not to look upon a noble life as an enterprise or trade, but to be a true benefactor and to do everything only for the sake of love for God." —St John Chrysostom
"When one returns to the Greek; it is like going into a garden of lilies out of some, narrow and dark house." -Oscar Wilde.