Did this HA 3 times without completing to farm for the collectibles tonight. Each time I got to the point to spawn the collectibles, they all were somewhere on the main island you zone in from Katta. Could have just been my luck, but so far the only place I've seen them. Went 4-4 grabbing them each time I ran it.
EDIT
After completing this 5 addition times that day after I posted this originally, I can confirm that all 4 collectibles always spawn somewhere on the island mentioned above. 8 out of 8 runs going 4 for 4 on them seems to good to be pure luck of the draw.
Edited, Feb 20th 2015 4:50pm by wfitz1491