My thoughts are: It's so interesting and a cool concept but it play horribly.
I really love the fact that the devs are trying something completely new and it will prolly not last for 2 weeks. But the event today is kinda game breaking.
Yes the cultists and the summoning circle seems to yield alot of good loot. The Cultists also actually have foot steps. Not sure if this is intentional or not but it's very welcome when these guys can be anywhere.
My issues are:

Trying to snipe or do anything? well now it's black and you can't see shit.
Got a LedX and want to extract, oooops no can do gotta cross the map on the other side. I know you were extracting but someone killed the boss that doesn't give XP or loot( and might punish you for trying to reach lightkeeper later).
Oh you're playing on reserve got a shit ton of loot and now want to extract, sorry someone kiled Antler man 30 sec into the raid and your only extract is now the fucking train.

I've also seen a vid or discription where it says that Zryachiy (or Antler man) will be passive up to a certain range and then when shot or when you're too close he'll attack. But he has walked into me 3 times now completely randomly and started shooting. (And I'm actively trying to ignore him)

I get the concept but it plays out so bad. My thoughts are that the devs are are onto something when it comes to experimenting with new events and not just "Fire Sale" and raiders 24/7. But this alters the game alot in a way that can feel daunting.