The "Ritual Staff" technology available to the Puppets of Misrule has no effect on Chosen of Tzeentch (Halberds).
I compared a unit at rank 0 to a unit at rank 1 (as well as to all the others in my army, the one-rank difference just made for an effective comparison), the unit at rank 1 had 1 additional melee defense due to its additional level but nothing else as seen here
, when the tech should have increased its MD by an additional 1. Also, all Chosen of Tzeentch (Halberds) at rank 4 or higher do not have Expert Charge Defense as seen here
I checked in my other army, which has only Marauders of Tzeentch (Spears), and confirmed the tech was working properly there, all units get the extra +1 MD per rank of experience, as seen here