And Volrath himself was Dragon to Yawgmoth, until he was replaced by Crovax (and, later still, Tsabo Tavoc).
Technically (at least according to the novels) Tsabo and Crovax were active at the same time, not to mention a Phyrexian-augmented Ertai, running about causing havoc. So it's more like a case of triple Dragons, no? Also, in that same block the 5 Dragons were awakened, each of whom had their own Golem Attendant, that could be considered their own Dragons.
In Kamigawa, Lady Masako the Humorless serves Emperor Konda as administrator, and she's a rather harsh mistress. Oh, and despite the trappings, she's not Konda's wife.
Konda's servants dared not neglect their duties for a moment under Masako's icy gaze, knowing that what she saw, Lord Konda would hear.
In Conflux, Nicol Bolas (the Big Bad despite being a literal dragon) has Gwafa Hazid, Malfegor, and Rakka Mar as minions, but had to go for something extra special to lead them - Sarkhan Vol, a psychopathic, dragon-worshipping (and perhaps Brainwashed and Crazy) planeswalker. He also has Tezzeret, a planeswalker he has rebuilt after said planeswalker was Mind Raped and left for dead by Jace Beleren. Bolas has saved Tezzeret from death twice, so the latter owes the former a significant debt, albeit grudgingly.