Dark Knight 4th job skills

Sweeping strike 4th job skill seems weaker and slower than spear crusher (3rd job) Dark impale is same lines of damage as fury and only slightly more damage, while hitting only 1 mob instead of 3. Due to boss summons, this one also feels very underwhelming compared to 3rd job ability Beholder is also a bit underwhelming to summon, maybe it could be given an attacking skill to make it worthwhile to cast?