Reading docs on decals and seeing that decals are not supported on skeletal actors. Is it still the case? (think damage marks, blood, etc.; it would be odd if it is the case, since Doom 3 supported decals on skeletal meshes)
Thanks.
Decals work on skeletal actors but they do not properly “stick” to the mesh as you can imagine.
You could fake it via a material or attach the decal on a bone (that will not always look right).
(btw Doom 3 is not really relevant 
not a UE game).
Do you happen to have an example showing flaws ?
It’s quite relevant since id Tech 4 is the engine from 2004! So UE4 should do better in 2016 
Deferred decals have been said to have issues, but… a possible solution could be the Left for dead approach, make sets of damage textures which are uv mapped to the the targets main texture, and triggered by damage to that area.