And i decided to give it a try as i never got my achievement and toy while it was current.
Steps:
- Queue for Highmaul Coliseum
- Accept queue after you waited for AGES
- As soon as you got into the instance, logout of wow
- Stay logged out until you think enough time have passed for the instance to have 'reset' - I was logged out for 1 hour and 15 mins, as i was cooking dinner/eating, i dont think you need to wait that long tho.
- When you login again you should still be inside the instance, but all alone in the instance, now go to the elevator, after about 30 seconds of waiting it should say something along the line of "match starts in 3 mins" - When the 3 mins wait have passed, the elevator should now take you to the top, after a bit of RP it should say something along the lines of "match starts in 2 mins" - when the match starts, you should instantly win the coliseum and get your achievement.
Screenshot of me winning:
As of patch 8.0.1 Blizzard made the old Highmaul Coliseum available to level 110 chars, you might need Gladiator's Sanctum level 3 in your garrison to be able to queue up for the Coliseum, as the level 3 building spawns the NPC that you have to queue at.
Im not entirely sure if you can just go to the npc in Nagrand and queue from there in case you dont have level 3 in your garrison, but that might work aswell, i already had level 3 tho so just used my garrison.