Don't worry, that achivement is not even cross-faction, so you can do it again on horde side ! Yes, thats how I understood it by logging into my hord that Im going to lvl soon (tm) - Hord/ally faction...whatever you play, has so much fucking content its absurd...
This is my HORD-SPECIFIC LIST I NEED TO DO: *cry*
Hord: Kuafons Harness mount, Voldunai exalted, 750 medal mount + 125 medal toy...buy on ah?, Natal exalted, Talanji exalted, buy hawli’s spicy chilli vendor, Darkshore/war campaign toy Brynja's Beacon and dark ranger round up, Emmisary Talanji expedtion, Voldunani supplies, Zandalari empire,
https://www.wowhead.com/npc=129354/rhanka#comments toy NPC, Griftah vendor toy, A way out (do war campaign) for worn cloak toy, paragon toys, Troll allied race mount,
sorry for messy copy-paste...but thats the list. I figure its like 400 hours of content....sigh. Other expansions never even had like 10% of this.