I think it may be better to think of a common, pan-Hellenic literary language that could be colored to a greater or lesser extent, depending on genre, Doric (for choral poetry, including dramatic choruses), Homeric/Ionic (for long hexameter poems and elegy), Ionic or Attic/Ionic (for history, dramatic dialogue, iambus), etc. The differences among these "colors" are really not that great and once they're assimilated, it's not too hard to recognize them in reading. Homer was of course the basis of instruction in schools throughout antiquity (and beyond), and Pindar was an instant classic who was intelligible and widely appreciated throughout the Greek world, not just in the "Doric"-speaking parts of Greece. In other words, this was pan-Hellenic poetry. Epichoric or local spoken dialects would have been quite different and much less widely intelligible outside their home territories than the literary dialects.Choral lyric was composed in 'literary Doric', an artificial dialect with a Doric flavor but containing also Aeolic forms from north Greece, and a very strong influence from Homer, which means not only an addition of Ionic, but also archaic features such as the masculine genitive in -οιο. Pindar himself coming from Thebes, his natural language was the Aeolic of Boeotia, but little evidence of that has been found in his poems; and it is a striking fact that, superficially at least, one cannot find much difference between his language and that of Bacchylides, who was an Ionic speaker from the island of Ceos.
The most obvious feature of literary Doric to our eyes and ears is the preservation of the original long alpha which had become eta in Ionic (and so in Homer) and for the most part in Attic. This gives a pervasive tone to the poetry, as it does, more surprisingly, to the choruses of Attic tragedy.
Later, in the Hellenistic period, Alexandrian poets such as Theocritus and Callimachus made a self-conscious effort to fashion hexameter poetry in a Doric-colored language, which nevertheless still seems to owe a great deal to Homer--Homer with long alpha. I think that Doric hexameter poetry, at least at a "high" literary level (as opposed, perhaps, to occasional verses, e.g., composed on the spot at symposia) would have been an inconceivable violation of decorum in the earlier age.
Maybe Michael could exercise some adult supervision over my ramblings here.