This data is misleading a little bit, because paladin is the most popular class and Demon hunter can only be Blood Elf on horde. (Although there is an overwhelming majority of Night Elf Demon Hunters)
This boosts Blood Elf numbers by a lot. It’s not because the racial is good.
But you just know, if Night Elf ever get to roll paladins, which I am sure will eventually happen, there will be a massive migration to Nelf Paladins for Shadowmeld.
The same thing happened with mages and warlocks when they finally got to roll them.
You’re posting this as if druids by default haven’t been able to do this before the buff. That’s existed forever. It existed on Tauren so long as you could drop combat.