A Visual Guide to the Bone Dragon in Crystal Tower

[Huginn]

By setting the skeletons at a distance of 1 arena radius from the dragon, you:
A. have the shortest possible route for a skeleton to take from the perimeter
B. do not have a tactical priority for skeleton kills.
C. run the risk of skeletons being dragged in two different directions, resulting in the skeleton staying nearest the dragon.
D. fail at mathematics

The most efficient way to deal with it is to take the dragon to the perimeter and kill the skeletons on the perimeter starting at 90º from the direction of the dragon from the center and working your way to opposite the dragon, with the remaining skeleton either killed on the perimeter pad closer than 90º from the dragon, or better yet, in the area between the perimeter pads.
This ensures that every single chord vector that the skeletons will take toward the dragon is GREATER than the radius of the arena, with the exception of tactical priority #1 skeleton which is closest to the dragon, unless said skeleton is killed between the perimeter pads, in which case ALL chord vectors will be greater than the radius.

Please learn mathematics, specifically, Geometry

Or just say that moving enemies is an exploit