Let's begin with a little detour.
The first time I encountered the concept of a femme fatale worthy of gods was in Star Trek: The Next Generation. In the episode 'The Perfect Mate', Famke Janssen plays an empath named Kamala, who is able to feel and conform to the desires of other.
With such outstanding empathic powers, she lacks some standard means of character development; she is required to mold herself to a particular other.
(At the end, she chooses to imprint herself to Picard, but nevertheless leave with her predestined husband to prevent a war. Sad...)
Was Hwi Noree the perfect god-trap?
She wasn't perfect, but good enough.
A perfect god-trap would a perfect mirror, but unless the targeted god is perfectly vain, it would also defeat its own purpose: a perfect mirror would be devoid of any (independent) persona which would stain the reflection of god's gaze upon it. A lack of persona would mean boredom.
One thing Leto hates is boredom; therefore a flawed mirror-soul is much more perfect in his eyes than a flawless one.
Therefore, Hwi wasn't the perfect god-trap, but exactly good enough.
Leto allowed himself few weaknesses, but cultivated what I call 'calculated frailty':
The decision not to search for the moment of his death in time, his un-humanness (and ultimate humanness) in a human world and the nostalgia of what could be, the loneliness and the desire for understanding and Love.
If he had discarded these weaknesses within himself, not only would he lose the approval and Love of his only source of power - himself, but he would also lose his reason in maintaining the Golden Path.