ALL the problems you describe stem from the simple fact, that the people in your raid struggle with grasping very basic concepts of positioning and movement. The only solution is, to become better.
Secondly, even if you get 3 people to run away, and stack the rest, Thoks movement during and shortly after he fixates is not 100% predictable. He sometimes turns for a split-second, or faces somewhere else, more than enough time to eat someone out of position. The ONLY safe way to do it, is to get the hell away from him while he still decides who might be the most delicious.