The acid test for a de-esser : “Herbert” from the vulgar cartoon “Family Guy” …
To remove a whistle each band has to be about 100Hz wide , or less, within the whistle frequency range.
At that high-resolution, processing on my (five year old computer) take several times the duration of the track,
standard de-essing which only requires bands say 1kHz wide is a lot quicker: less than duration.