I would say Witchcraft is mostly a utility skill, buffs, debuffs, summons, destroy summon, with some damage, the biggest one being Death Punch. Why yes, I would like to deal 1000 free physical damage to an enemy with one spell.
I admittedly didn't use witchcraft in my first playthrough, but after I specced Jahann in it, it definitely helped the party. Madora + haste + rage + oath of desecration + flurry = massive damage. I would say on it's own Witchcraft doesn't seem too strong as a source of direct damage, but the ability to buff allies and weaken enemies is incredibly useful. Give your assassin a damage boost to make his backstabs even more lethal, or make the enemy's damage dealers miss their attacks or deal less damage, turn the enemy tank's plate armor into little more than scrap.
