Judge Lamberth said, in one of his rulings, that the rights to dividends is an important stick in shareholders' bundle of rights and that the NWS removed that stick. It certainly has value, which is the entire point of the trial.
In terms of economic rights with regards to the company, both junior pref and common shareholders really only ever had dividend and liquidation preference rights, each of which were extinguished forever by the NWS. At one point common shareholders had voting rights too (with respect to the operation of the companies), but those were removed in 2008 when conservatorship started, not in 2012 when the NWS was signed.