Caches can help speed up playblasting on objects that your not working on. e.g. if your working on character or object x cache other characters or objects to make things work faster for you.

Also eleven isnt a complex rig but is there not a lower level of detail you can switch to. Its got alot of complex skinning going on there that it has to calculate every frame, most rigs have whats known as a 'can' mode which is just the orignal model split up and parented or constrained to joints rather than skinned. This will be able to play fluidly, at least thats what we do here.

With a cans displayed rig its just calculating transformation matrixes for each object where as with a fully skinned / deforming rig its doing a lot of math to work out where each vert should be, often its fine but it depends what kind of expressions are going on and how many layers of deformation there are.