You diagnosed the problem in the first sentence. I have a feeling that all those people who complained about their Hyper carbs sucking, and needing to use an OS carb instead just didn't realize that their high speed needle o-rings were worn out (which these carbs do pretty quickly for some reason). Order a set of those, and follow the link above from the OFNA forums which explains how to tune the midrange needle for the carb, and you should get back on track.

EDIT: Apparently HoBao (if they are the ones that make the Hyper engines) realized that there needed to be a change to the seal design. When you order a set of replacement seals they are much thicker than the ones that come installed on the carburetor from the factory.