Drag Race

If you're worried about accidentally completing the world quest before you do the achievement, you can mount cooper, invite a friend, convert to a raid, that way you won't get quest % completion, so you can freely try as much as you want 'til you get it! Remember you'll only see troggs once you've got credit for the mount cooper part, which needs to be done in a party, then switch it to raid.

Use [spell=253494] ability on troggs to drag them, the point is to drag 5 of them at the same time.
After using [spell=253494] you have to ride over the trogg to throw a rope.
Troggs are taking huge damage and die rather quickly so you have to find a place with a lot of them.
I was able to do it in the north part of Norwington Estate near the dance floor.
You can do this achievement while doing No Party Like a Trogg Party quest in main Tiragarde Sound campaign A Sound Plan.
Or you can do it later, there will be a Trogg Tromping world quest with the same mechanics.
Drag Race video: https://www.youtube.com/watch?v=4-KUDxsfKJY

Near where you pick up Cooper, I was able to aggro 2 patrols that were just walking around without attacking anyone. With these 2 following me (not using Bolas yet) I simply moved close to where 3 other troggs were fighting NPCs, and got the achievement very easily.

So my recommendation to anyone trying to do this, is to run around and locate 1-2 troggs patrolling the area and try to do it nearby.