A Targaryen Kings of Summer Deck made 3rd place in the Spanish Nationals this year (74 players, probably Europe's top meta).
The deck used 7 Dragons (1 x Balerion, 1 x Drogon, 1 x Viserion, 1 x Rhaegal and each of the Hatchlings (non-shadow) as well as Daenerys (QoD).
With Black Ravens, 3 x Myrish Villa to get out expensive cards and early-game control cards such as The Hatchling's Feast (with TftN) and Flame Kissed (also dragon-themed cards, aren't they ?) the deck was able to stall until the big guns (= dragons) could take over.
I don't know if that is a "Dragon Deck" in your eyes, but I think its pretty close to one.
Of course, it was run by an experienced player who knew his deck inside and out.