As for the Tahirids, Saffarids, Samanids etc., Wikipedia's History of Iran article has them down more accurately as "Iranian semi-independent governments". They were regional dynasties under the Abbasid caliphate. As Michael Axworthy explains (Iran p.87): "The first of the regional dynasties to establish itself as a real rival to central authority was that of the Taherids of Khorasan, followed by the Saffarids of Sistan and the Samanids - all dynasties of Iranian origin. The Samanids were based on Bokhara and the region around Balkh, claiming descent from the Sassanid prince Bahram Chubin. Each of these dynasties (especially the Samanids), and those that followed (notably the Ghaznavids and the Buyids), tended to set up courts adorned with Persian bureaucrats, scholars, astrologers and poets in imitation of the great caliphal court of Baghdad, as enhancements of their prestige, and as a disguise for their tenure of power, which otherwise might have appeared as more nakedly dependent on brute military force."