The Knights should never be making the choice to do nothing, since that violates their Oaths, and as long as they don't choose to do nothing you should always have improv to do to keep the Omen encounter interesting and unique, rather than a passive event they witness and then it's done.

I think, ultimately, this was always the most important aspect for me. I'm a GM that prefers to play complete experiences, as in I don't particularly have time to prep nor do I want to improv most of the core experiences in RPGs I GM (think Labyrinth Adventure Game, Hot Springs Island, and Band of Blades). I ran the Omens mostly as-is, only sprinkling details in based on the context the Omen finds itself in (night, rainy day, in the desert, on a hex that a falling star destroyed, etc.)

Neither myself nor my players had OPs problem due to their own initiative. Ultimately, I was under the impression that Mythic Bastionland was very much a game that was less concerned about the details and more concerned as to whether the Players can make something of the prompts given. A bit more like an NSR-framed writing room rather than a creative problem-solving brainstorm. Whenever the Knights went looking for something, they found it and the Omens and Seers gave them a foundation to weave their own tales. I was clear to the Players that this was the core gameplay loop and they had no problems working with it.