Yes it didn't exist for the wast majority of their history.
All female druids appeared in the last ~46 years (30y from WC3 to first WoW events + 16y to current WoW, if I get that right).
However there were always exceptions who were tough druidism while being a priestess or warrior.
Then there are cults, let's take Druids of the Fang who were amongst the first to succumb to Emerald Nightmare (I wasn't joking that the lore of EN is as old as WoW).
So a druid of the Swarm is probably amongst those rare cultists, plus she's based on a Hearthstone card and Elerethe Renferal who only became Druid of the Nightmare relatively recently.
Most importantly however it's a sexy model, and I wanted to try this idea of a web cape