In one of the calcified fragments it talks about how our world isn't very kind to Ascendant beings. Something about our laws of physics not allowing full manifestation of their power, which is why the Hive build throne realms. Crota was walking around in our world when the moon take overrun by the Hive, and Eris's fireteam went down and slapped him back out of our dimension but they couldn't finish the job. When we killed Crota, we broke into a crossover dimension between his world and ours. I imagine the "eye" in the sky during Crota's End is a gateway to his throne realm. That would explain why his oversoul comes out of it. For Oryx, he was powerful enough to split off several copies of himself to oversee his war effort in addition to maintaining his own strength. For the most part his Echos were harder fights than Oryx himself so it's possible that the bulk of his power was invested in them, kinda like Sauron and the Ring or Voldemort and his Horcruxes. And when we chase him into the Ascendant realm to finish him off he's probably still picking bullets out of his chest. I think Oryx was plenty powerful but also highly cunning. The calcified fragments make Crota out to be very focused on killing stuff and the Deathsingers being obsessed with exploring death, but Oryx has a much wider vision of conquest. Even the Darkblade, who tried to kill Oryx and take his crown, was only imprisoned because Oryx knew he could still be useful. tl:dr Oryx is smart and his kids are dumb.

[spoiler]holy shiet it's another bump[/spoiler]

[spoiler]Discussion Bump?[/spoiler]

Crota was tougher His daughters were weak AF it's just the shield that gave them power

The gatekeeper could out do the first oryx you face