after kings rastekahns death in daz'alor, his daughter talanqi took control of the zandalari, becoming queen. keeping her pact with the horde she joined the horde.

The clever fox-like vulpera were driven close to full slavery by the sethrek. when the horde saved them, they took a place among the horde.

after elisande of the highborne elfs betrayed azeroth by allieing with the demons of the burning legion their society fell, millons of years later they joined the horde after killing elisande.

The shamantic taurean of highmounten were recently aided by both the allaice and horde, but they joined the horde instead. 

the uncorrupted orcs of the prime timeline were renamed to mag'har, they fiercely fought alongside horde allices to escape draneor.