The greatest reason Rowan left his Ouroboros Bloodline at Level 3—The Rift State, not even the peak which was at the Incarnation State, was not just because he wanted to push this bloodline potential to its maximum, that was the plan at the beginning, but now he also wanted to rid it of its greatest weakness before making this bloodline more powerful.
That weakness was the Intent of Chaos. Rowan could no longer bear the thought of being filled with the Intent of another Primordial, because for him at this time it was pure torture. After all, he could feel it more deeply, both the Intent from Chaos and the other Infernal Intent inside his Angels.
They were like maggots crawling inside his eyes and whispering words of madness in his ears, he needed them gone from his bloodline or else he might go mad.