Step 16 - Don't have to be at the center. I was just on the outskirts on the south side of ring and they spawned coming from the east.
Step 20 - There are 2 Lcea Katta in zone. The one needed for this step is on the west side of the druid rings.
Soloing this to get the AC aug (which I still haven't seen in 7 tries) the only annoying part is the respawning skeletons task. The trick appears be to kill the chromatics until they turn into icy and then don't kill any icy's! Because they will respawn as chromatics and the cycle will continue! I'm