Tried again last night.
Couldn't find a group but a nice guy heard me asking for a long time and logged on his 50 necro.
We pulled the 2 dogs away from the Summoners. In the pillared path maybe 5 horselengths away, if that. Killed them.
I approached the Summoners, I read a message about the summoning beginning and (immediately - didn't really READ the text) backed up like was told so as not to aggro them.
We fight 2 gargs. They die. However, during this fight - for whatever reason the necro's pet was by the summoners along with my helper. But he mentioned (and it both made sense and worked out that way

) that he wouldn't aggro them.
In the end, after gargs died we waited. I tried stepping into radius but while more spells were coning out - no message. Eventually, they aggroed me and I evacced us due to our not being able to affect them.
I have NO clue what was done wrong this time. This makes a couple weeks pre and post hiatus on this and no less than 10-12 attempts, possibly more - remember the delay before it 'resets' btw - this is a LONG time spent on this.
I know I haven't played since March (birth of my son) but I'd have expected the DEVs

to have worked on this event to clarify/fix it a bit
