A Draka paradox, which opens a metacosmic black hole that would eventually consume the entirety of the Warcraft metacosm leaving only a scintilla which may or may not spark an entirely new universe.
Realistically, I have no clue. Although if individual strands join the composite entity reflexively then I would suppose a "new" Draka journeying into the Shadowlands would never be afforded the chance to kill the composite entity before joining it. Another example of a plot hole would be an irredeemably evil Draka from some other continuity were to merge with the existing Draka in Maldraxxus, thus changing her alignment slightly or something. Although I suppose the Arbiter is capable of discerning if that is possible during the initial judgment.