Solo darkness is one of a DNC's best damage tricks and Kleos is invaluable for that reason alone. Outside Abyssea, I find it stronger than Evis, so I reverse doctorugh's SC above and close with Kleos.
It also reduces mob evasion, which has situational use. This can actually dispel weaker evasion increasing effects, replacing them with evasion down, in the same way that haste can override weaker slow effects.