This is a known issue and will eventually be addressed:
This is not the case: Doppelgangster has not been changed, and I myself put it to good use in my Handbuff Paladin just yesterday.
You must be thinking of Saronite Chain Gang, which was indeed nerfed to summon a fresh 2/3 Saronite Chain Gang instead of a copy, in December 2018. This was to address the self-duplication interaction with Shudderwock, but of course it also nerfed the handbuff interaction.