A big issue for Dark Eldar is a severe lack of Plasma-equivalent multi-shot 2+ dmg guns. The only one is the Disintegrator, and they're only available on vehicles: Ravagers, Raiders and the aircraft. Which is the reason all Dark Eldar lists I see start with "3 Ravagers, 1-3 Razorwings".
Upping the damage on weapons like the Splinter Cannon could help alleviate this... if they didn't also halve the shots at close range and make it so infantry can't move and shoot without penalty. Because when I think of Dark Eldar I think "static gunline".