How to get to Tharillon in the quest The Spade's Blade:

Start near 25.6, 27.2 in Suramar and continue up the path:

Keep following the path upward as shown below:

There will be mobs all through the way:

Once you get to the area shown below, there will be a flight of stairs near the lower left area of the image; take the flight of stairs down and head toward the building shown in the picture; the building has a back exit through which you get to a garden. Take that exit and head right,
and soon you will see the NPC you need to kill (Tharillon) kneeling at the right corner of the garden (shown in the image below this one).

I used an invisibility potion to get through all the mobs; alternatively, you can run as far as you can toward the NPC, die there, and release near the
cliff on the far side of the garden.

The following image shows the NPC you need, where you came from to get to him, and where you should stand in order to pull him:

Finally, an image of the same area, where I have zoomed out in order to show where he is located more clearly: