The Covens book uses an entirely different chart. For the uninitiated, the Power From Pain rule is essentially a clock. On X Round, you get Y benefit for all models in the army that have the Power From Pain Special Rule. Unlike before, there's no need to kill a darn thing. You just become progressively more frenzied by the blood orgy you're perpetrating (more or less). The Power From Pain chart for Dark Eldar grants (eventually) Feel No Pain, Furious Charge, and Fearless (and even Rage if the game goes that long, which IS new to the new Codex:Dark Eldar) to the models with the rule, just as before only on a clock.
Fear is the Mind Killer...
This coupled with Fear makes the units in the force have a real chance of actually affecting the enemy. This could be the difference in an assault at a critical time against an excellent melee unit. . Units that have And They Shall Know No Fear (ATSKNF) or the Fearless special rule won't care. However there's a lot of units that will be affected.
Aside from that, normal morale checks will be affected in any event. This ability dove tails nicely with any Dark Eldar who ally with the Coven with their Armour of Misery and its aura of -2 Leadership. The combination of the two could make the Soul Fright ability of Torment Grenade Launchers extremely valuable (albeit again, not to Fearless units or those with ATSKNF). The Torment Grenade Launcher act like a Psychic Shriek type of attack that is done on normal 2D6 and of course isn't psychic. Even without normal Dark Eldar allies, one must admit that Fear can be a real X factor for this army to wield.