I had a look around on the PTR and started playing with the map images in photoshop to put them all together.
First 6 bosses :
And the route to follow :
Boss 7-9 :
Boss 10-12 :
For the heroic only boss we have to go back to Primordius, he stood on a grid, which will disappear I assume after you kill Lei Shen on HC mode. --> this leads to a twisting staircase downwards.
And the whole map :
Anyone who gets lost is a baddie!
And the PS file, for those interrested : https://www.dropbox.com/s/5eletmeqwqp22fi/tot.psd