Stephanie C. answered 06/22/19
B.A. in English, University of Arizona, specializing in literature
My 3rd edition of the Oxford Dictionary of Literary Terms includes "cosmic irony" under the entry for "irony" and I would consider this a reliable academic source. As long as you flesh out your argument sufficiently, there's no reason using this term should weaken your writing.
The excerpt from the entry reads, "The term cosmic irony is sometimes used to denote a view of people as dupes of a cruelly mocking Fate, as in the novels of Thomas Hardy."
Baldick, Chris. "irony." The Oxford Dictionary of Literary Terms, Third Edition. Oxford University Press, 2008, pp. 174 - 175.