I agree about her lower register being very low but its not her technique, she just has to be right on the mic as it's a quiet tone.
I dont overly mind that she come across boring because her voice and vocals are GREAT!!

Not sure this cover suited her as much but like the dark themed arrangement.

She is a under appreciated vocalist because she has defo one of the best techniques out there in the industry 2day.
She is made for pop ballads, slow ballads, R&B, soul & some rock ballads as well.
Leona can sing various genres but those are her strengths for me and the club sounding pop waters down her vocal ability, if song is not on her wavelength.