here is some my opinions, Eternal night set work pretty good with all HUnters since LE got nerfed. (it still deals high DPS on single enemy tho), Special of storm render doesn't hit to some enemies (it's depend on enemy's vertical hitbox) and that special doesn't hit to x3 enemies at once.
Ract/cl with charge yas9k is OP especially in tower. Armageddon sometimes targets enemy that you don't want to attack (guard form epsilon etc)
About Exterminator, it's depend on area/your team i'd say. it works well at some situation, but i agree DVL is much better than this weapon.
in addition, actual special of FEB is fire bullet + explosion, so it hits 18 times on targeted 1 enemy with 1 combo.