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