I had found a recipe to make homemade Tootsie Rolls which was essentially just chocolate taffy. I've tried it a few times with the same result; it turns into basically a somewhat chewy hard candy.
I'm not a candy making expert, but I think the problem might lie in either the heating of the mixture (ie- getting it to the right temp for the type of candy it is) or in the pulling.
Does that sound about right? Are there other things that I can check when making taffy that would turn it into a soft rock?