if you use dmx format, the model should face to -x axis.
and the target up axis shoud be y axis
when u export mesh or anims, u need to rotate your mesh or anims to fit the above options.

i use sfm to export the hero's animation as .dmx file, then import to blender, and export as .smd file by BleST scripts.
However, i found the animation have less frame than normal valve's animation.

here are the results i tested.
https://imgur.com/a/7gdtHng

any idea what happened?