Ok here are two videos. The one I was talking about is from a group called Proper Bird. The other is from Fatboss.
Both seem to say the same thing. Sorka will not Blade Dash anyone that is more than 45 yards away. Anyone hit with Blade Dash gets a debuff. Sorka will target debuffed targets if any are in range. SO:
1) WHOLE raid except one tank and one ranged stay at the entrance. The tank with Sorka must take her ALL THE WAY into the other corner. Ranged shouldn't need to be all the way over, just within 45 yards. Perhaps Sorka wasn't all the way in the corner or some raiders weren't in the right spot.
2) Doing that right should give ONE person the debuff. That person can't be in the group or the Dash will spread the debuff. The target needs to stay out. Sorka also needs to be ALL THE WAY out and away from melee to avoid spreading the debuff. There is enough warning with DBM timers that we should be able to move Sorka back and forth, but we could also just leave her and have Ranged hit her.
That should be enough. Should keep the Blade Dash going to one specific spot. Also need the first target of the Blood Ritual to go to Red X and STAY THERE. So long as that's the only person with the debuff, that is the only person that will get targeted by that ability. If both of those work as expected, the rest of the fight should be pretty easy.
It's up to Sanzaru, but I think it would be worth it to try keeping sorka separate at least for one pull.