Hey guys! I know I'm a bit late to this post but I just manged to complete this story quest with a guild mate and that changed some things. Before I only had 2 krait spawn in the water to the left of the tower, and then 2 that came up from the water behind it. When I went in with a guild mate, 4 krait spawned in each location so I believe thats what I was missing in all the 6 runs I did previously solo. If you are still stuck on this one, try to get someone else to come with you! It might set the instance to a "completable" state. Good luck!
