If you put one skill point into Augment Damage (though it will only boost melee attacks), you should get the second skill level the next time you reload the game. You can randomly get either a level Augment Damage or Augment Defense from a quest in the Dark Forest.
I never tried Embrace Shadows, but I believe it is based more on the ambient light than the type of enemies in the area (getting near a light source, opening a door or running out of stamina will reveal your character). When hiding it is possible some opponents may notice you more easily than others, but I don't recall anyone mentioning that, so it is probably not a significant factor. You could try saving the game, then put a point or two into the skill and try it out. If it doesn't seem helpful, simply reload.
Alternately, try out the survivors special skill, Sneak, which does basically the same thing (though there are a couple exploits with Embrace Shadows: <span class='standouttext'>Spoiler : </span><span class='spoiler'>cast the spell on an NPC or opponent to turn invisible and steal indiscriminately [as long as you stay in the dark, so put out any candles, etc first], or attack without triggering a counterattack</span>: highlight the text to read). Those exploits could make the game too easy, so use at your own risk.
