Okey let me drop it simple obviously you struggle to see the problem so let me explain like you have a syndrome.
HD does true dmg(aka its not getting affected by dd/mdef/pdef etc) so it always hits the same (and its based on magic but when it ignores everything you can say its true dmg unless you have magic reflect skill which would nullify the dmg thats the only thing that can affect it, unless they completely changed it which i doubt since the core of the skill is obviously there, but it still wouldnt explain the missleading huge numbers differences )
Why its wrong:Example So you have 117 magic attack HD says lvx 114% from your magic attack restoring 107% of your final dmg as hp(the description is bullshiet) but you dont need to be genius to see 114% that : 114% of 117 attack is more than 117 dmg to mobs or something close to that number- but in reality you hit 14dmg what this result tells you ?