The Collaborative International Dictionary of English v.0.48:

Tragedian \Tra*ge"di*an\, n. [Cf. F. trag['e]dien.]
   [1913 Webster]
   1. A writer of tragedy.
      [1913 Webster]

            Thence what the lofty, grave, tragedians taught.
                                                  --Milton.
      [1913 Webster]

   2. An actor or player in tragedy. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tragedian
    n 1: a writer (especially a playwright) who writes tragedies
    2: an actor who specializes in tragic roles

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "tragedian":
   choreographer, comedian, dramatist, dramatizer, dramaturge, farcer,
   farceur, farceuse, farcist, gagman, joke writer, jokesmith,
   librettist, melodramatist, mimographer, monodramatist, play doctor,
   play fixer, playwright, playwriter, scenario writer, scenarioist,
   scenarist, scriptwriter, tragedienne