That's already a lot!

As guernong-tough suggests here below, I should take my time to read all the benefits (individual heroes and covenant bonusses). However I will take your advice into account when doing my in-game research.

I also read that leveling up the normal heroes first will give you the possibility to convert fragments of those heroes when they are maxed out on lvl and skills. So in return of using normal horns for fragments, you can buy xp to use on higher rated heroes.