Sadly at this point in time, my observation is races just exist for destruction shock factor and advancing the faction narrative. Your baited into them in their intro, then they don't really matter.
Outside their function of an interesting identity to pick up, they just cease to matter outside their introductory expansion... without fail.
The races introduced in the RTS have not had focused progression outside those games. Every race that was introduced had positive focus then, as well as problems, but afterwards - were just tools to furhter the horde/alliance faction narrative.
WoW became all about the factions from TBC onwards, Classic was about the races and the zones. You got lore, not development, but their presence at least was a progression from the RTS.
Really think about it:
Humans, Dwarves, Gnomes, Night elves, Draenei, Worgen, Pandaren
Orcs, Forsaken, Troll, Tauren, Blood elves, Goblin
None of these have had serious progression outside their intros in wow, whether they were introduced in classic or after. Cata was the only time that happened, because it re-did classic. You get introduced and then you're just a horde/alliance tool