What the Draketooths should be able to deduce is that the same force that took out Dorukan's gate also took out Soon's, because the Cloister on Dorukan's Gate faded after Dorukan's death, and then was restored; faded again after Dorukan's Gate was destroyed, and then was reestablished over Azure City after Soon's Gate was destroyed. They may not know it's Xykon, but they know it's bloody strong.
We don't know that Zz'dtri would be able to pinpoint things that closely. We don't know that the ziggurat would be scryable. And we don't know that the Draketooths would be caught with their pants down if the Linear Guild teleported in, even if LG didn't get immediately caught up in the surrounding illusions.
He knows there is a ritual. He knows he doesn't want to die at Malack's hands. That he actually wants to secure Xykon's ritual is far from certain.
And has a poor track record as far as Team Evil is concerned.
Redcloak probably hates both Xykon and himself. Xykon sees Redcloak as fun to toy with. It's not a happy family down there.