I've never annealed, so I don't know for sure, but aren't the cases supposed to either rotate or be heated from both sides so that they are uniformly annealed all the way around? Seems to me that design would only anneal about 2/3 around the should and neck.
Either works. Constant rotation would not hurt with multiple torches. I anneal using a small electric screw driver and a 1/4" drive deep socket that fits the case diameter I am annealing (13mm for 308 I think).. I plate the torch on the ground (on of course) and spin the case with the screw driver until color is correct.
OP: on the next one you could force the cases to predictably rotate by machining a ring of small serrations into the base plate that barely contacts the outer edge of the case head. So as the top plate with holes spins the outer edge of the case head drags on the rough surface of the base plate and spins the case the opposite direction the plates are spinning. Skateboard grip tape or something similar is another option for a textured surface.
How much money did you guys have into this? It is VERY nice and built pragmatically.