Divide and Conquer

So far, what I have been doing to get this is joining one of the raid groups in the horde (or alliance if your horde) base and standing at a location like Brute's rise, while they kill things all the HK's I get count towards this achievement because my location on the map is somewhere outside of the Road of Glory, there are plenty of locations that work, but as long as you are close enough to get HK's, it doesn't matter where the HK's happen as long as YOUR location is not on the middle road.

The water right below the alliance keep is a great place to get this, im at 1000/5000 and im on my 5th battle in ashran, Ill have this in no time in this spot.

Can confirm Snyderz comment and add the following:

If you can see the "Horde Slain:" and "Alliance Slain:" stuff at the top, you're in the Road of Glory.

If you're outside of that area by even a single step, you'll start getting credit towards this achievement.

Well I finally got this in 8.2.5 BFA. Its one big AFK fest if you wanna get it.

51.51 at korlok is great

52.65 is great if you are alliance and hord pushed us down to the base

55.34 is also good for the opposite if ally is pushing hord to their base.

Have some YT going or w/e, help out in the start at Inferno, call out tactics and try lead, and once the start is over you just AFK on these 3 cords. Horrible to AFK sure, but its the only way cause if you do it normally you might get like 9 honorkills that counts each fight...