Well... they said that to become an arrancar who resembled a human you had to be at least Vasto Lorde... because those below turned out like Grand Fisher, who most likely was an Adjucha.

And since the 'rank' is Vasto Lorde -> Adjucha -> Gillian.. it is not farfetched for the Adjucha to order them around.

Also... if Rukia was unable to hurt a Gillian, what chance would she have against Adjuchas, Vast Lorde and Arrancar?

Although about the power levels... I do wonder about Nel... wtf? Heck... 'good' hollows is still a little hard to swallow... weren't they all supposed to be 'fallen' souls or whatever?