Hey, I don't wanna start a war or anything. But I'm pretty sure there are more Mok'Nathals than High Elves. 
Food for thought.pic.twitter.com/5GygRffVA7
-
That's not entirely accurate anymore. There's plenty of NPCs and characters assumed to be Mok'Nathal. After all plenty of Mag'har relocated to Azeroth after the portal was re-open the same can be said for the Mok'Nathal. The Mok'nathal have a whole village on Outlands still.
The problem with Sin'dorei, Quel'Dorei and Ren'dorei is they further divide their races up just by existing. If you added them up all together they would definitely be larger than the Mok'Nathal but because they divide themselves they're in smaller factions than normal.