The Cassell Guide to Common Errors in English (p251) would agree with you. It states:
There is a tendency to combine 'more' (or some other comparative) with
'rather than' in such a way as to upset the grammar.
Among the examples the CGCEE lists is this one:
'The German appeal for an armistice was put to President Woodrow
Wilson in the hope it would get a better deal from him rather than
from Britain or France' (The Times). Here again the word 'rather' should
The same advice is given by The Right Word at the Right Time (p513):
Take care not to use rather than in place of than after more, simpler,
harder, and so on.
*He finds it simpler doing the sums in his head rather than looking for a paper and pencil. Either omit the rather here, or say simply He
does the sums in his head rather than looking for a pencil and paper.
The more recent Garner's Modern American Usage (p694) concurs:
*More...rather than. It's poor syntax to write more...rather than-e.g.: "His ideological convictions...were defined more by
present-day concerns rather [delete 'rather'] than by thirteenth-century
conditions," Robert E. Norton, Secret Germany 667 (2002).
Merriam Webster's Dictionary of English Usage (p798) lists various commentators who "notice a curious construction in which a comparative that you would expect to be followed by 'than' takes 'rather than' instead". The MWDEU gives a couple of examples of this usage and continues:
The reason for the awkwardness of the sentences is that the more in
each sentence leads the reader to expect the usual than, but rather
than turns up in its place. The existence of such sentences (which we
advise you to avoid) is good evidence that rather than is perceived as
a unit by many writers. We lexicographers will, in time, have to
recognise its existence.
So the usage guides are fairly unanimous that this is a construction to be avoided. And, as the OP suggests, a careful writer might not only omit the rather in New Yorker sentence but also insert a to for sake of parallelism:
I find it easier to use the serial comma consistently than to stop
every time I come to a series ... .
I myself, however, do not find the rather than usage particularly problematic.