Is talking about a ‘Public Figure’ considered backbiting ?
Re: Backbiting
YES 
Re: Backbiting
Yes, of course.
Re: Backbiting
Is talking about a 'Public Figure' considered backbiting ?
Here, talking about 'what' matters.
In Islam ... Backbiting (Gheebat) is talking something true about a person behind their back that the person do not like. If what one talks is lie than that is not 'Gheebat' but 'Bohtan'.
As far as I know: If public figure is politician wanting to represent people, then to talk about good and bad of that public figure that can affect people is not backbiting (gheebat), but it is spreading awareness.
On the other hand, life aspect of public figure that is personal and in no way affects public representation nor public need to know, than that should be avoided propagating as that could be considered gheebat.
Sometime people talk lies about public figures (do bohtan), then that is obviously not allowed.
Example: If a public figure drinks in his private life, then that does not affect his holding any public office, and if one comes to know about that then it is better to keep quiet about it, as talking about those things could be gheebat.
On the other hand, if a public figure is a thief, liar, deceiver, corrupt, do nepotism, is mentally retard, incompetent, etc … weather such be true or perception that got built around that public figure (with some basis of it being likely true), then it is better to talk about that, as such character or aspects of a person in public office could harm public, public interest, and public well-being … so public should know about it and bringing awareness to public is fine, so, as long as talking about that person is not to malign the person unnecessarily, but to give awareness (and warning) to people, one can talk.