@rayp: I have to add that bone animations are in fact much faster that vertex animations when done on the GPU (=> shaders), otherwise both are slow (and vertex animations need lots of memory).

@OP: yeah, stencil shadows were good 10 years ago because of the rather low amounts of polygons "back then".
For todays games you simply don't want to use these because both, performance and visuals, are really bad.
Before I forget: There are also lots of lighting glitches caused by culling, so I really recommend to use something
else, these shadows are as outdated as this engine.

Performance wise, Acknex is definitely not good in this area. Not saying that it's really bad but it's not lightning-fast
for sure, esp. when it comes to rendering. Lots of entities have a huge memory footprint and are also rendered slow
because of the missing instancing.

As a first step, leave shadows off and try to disable animations to see if that's the problem.