I have been killing the Gylton/Entalon spawn cycle for sometime but have come up empty after 20+ hours total. Since then, I have moved onto Nekenezna and Phurzikon. Here is what I found:
These are definite place holders:
wurm (the least frequent for me)
ember hornet
forest giant verdant
forest giant ancient
moldering gorilla
tattering gorilla
sarnak zealot (these were most common so far)
sarnak avenger
sarnak champion
greater war boned skeleton
greater plague skeleton
scoriae hornet
Once I found the place holder, it is very simple. -450, -2550. I have killed Nek/Phurz about 10 times so far and no embers, only guts for the Bard epic.
Spawn time is 78 seconds per mob... just like the Quillmane cycle!!!