No offense but only stupid tanks take him north and honestly deserve to die. If you say tanking him there leaves room for error then you're wrong.
1. if he is tanked in the center that means less room to travel when pulling skeletons to the edges.
2. tanking him north means that some skeletons will cross through the water meaning more damage on you and more work on healers.
3. tanking him north also means less room for dps to get positions on him and will likely have to go into the water resulting in less dps more work on healers.
4. If he is centered the healers can easily reach everyone.
5. group a should pull east while group b pulls west.
6. no one will get hit by BD's cones if no one stands in the front. Only stay to his flank or rear.