Summoning Ritual

Today we convinced a bunch of characters/players to help with this to attempt to spawn the rare which has a chance to drop [item=174874].

We first got the rares to spawn at 2:28 PM after some unknown number of clicks on the summoning portal.
We finished killing all the 3 spawned rares at about 2:32 PM.

We then repeatedly summoned multiple characters to click the summoning portal one by one following this.
Having clicked the summoning portal every time it spawned on at least 15 different characters, the rares finally spawned again at 3:02 PM.
We finished killing the second set of rares at about 3:05 PM.

Testing then with just a two-player raid group, the summoning portal is able to be repeatedly-clicked by the same player (assuming they have not already received quest credit for clicking the portal).

A 3rd set of rares spawned at 3:44 PM when clicked by a player in a raid group. Yiphrim finally spawned in this set, and all 3 were fully killed around 3:51 PM.

Then at 3:59 PM a 4th set was spawned, again when clicked from a raid group on the 3rd click since the previous set was killed and again with Yiphrim. This was only 8 minutes since the previous set was fully killed. We killed the 4th set of rares sometime after that...

And at 4:07 PM a 5th set of rares was spawned only 8 minutes since the previous spawn, and less than a couple minutes from even killing the previous set.

TL;DR From this research it seems that currently the following may be accurate:

• 
  
• Any click can spawn the rares, even when in a raid group, and without cooldown from a previous rare spawn it's just a low chance or possibly increases with each click? You know, the usual RNG
• 
  
• All previous rares probably need to have been killed Hard to disprove unless they can spawn without killing all prior rares, which has not yet happened
•