As part of the first team to ever do it, and possibly one of the only teams to do it, here's what it looks like:
There are 8 of them. They spawn with ever increasing health if you kill them one at a time (you had to kill a certain number as a roaming group before splitting up to do all 8 at once, I assume the prep is fixed) so you must solo 6, one each, and team up on the last two within the 30 second timer or they re spawn. If you touch the second two, or they see you, before all original 6 are dead, the original 6's "death timer" doesn't reset and you get rekt.
Credit to /r/raidsecrets and /u/ZPEvo for figuring this out and including me way back then.
A lot of people are asking/talking about strats to do it. Well, it depends on how they changed them. I can't see them keeping them the way they were, it would be too hard to coordinate with the nerfs to ghorn and shotgun crit damage. Most likely they will remove the respawn of them and keep/buff their current health and you'd move around as a team of six to off them. If that's the case get weapons of light+melting point/tether (these two don't stack!) and wander around with Raze Lighter. Raze Lighter has the highest burst DPS of any weapon in the game and there's no crit to mess up like you could with a sleeper. Also no reloads! The dark drinker is good on axis because of the multiple legs you hit at once. Stick with Raze and wander around messing them up! A well placed weapons lasts for 45 seconds with its perks active. That should be more than enough time to kill 3, so with two titans and a tether it should be easy work!
We'll know more when it releases. If they change nothing, god help the PUGs that attempt this challenge.