[Unam Sanctam]

Given that you don't mean to accuse the Pope of incorrect teaching, I think it highly improper, inaccurate, misleading, disrespectful and unnecessary to use the term in reference to the Pope. Heterodox means "different teaching", and thus would mean the teaching of heresy.

[ultima ratio]

I think it is highly proper to call this Pope unorthodox. Praying with animists to the Great Thumb is highly unorthodox. It is not formally heretical, perhaps, but it is not in conformity with traditional Catholic thinking either. It is indeed unorthodox for a pontiff to behave this way--and shocking--no matter how the Vatican bureaucracy tries to spin such actions afterwards. The problem this Pope poses is that no Catholic in his heart wants to even think about the evidence: that the man at the very top frequently does act--and teach--in ways that do not conform to traditional Catholic doctrine of long standing. His position on capital punishment, for instance, is highly unorthodox and breaks with long-held Catholic doctrine. Justice Scalia has weighed in on this not too long ago. The Pope's position can't be reconciled with past teachings of past popes or even with Scripture. It is, in a word, unorthodox.