Confessions of a Liberal Puritan

he was far too invested in his own needs and power to ever be redeemed. Everything was based on outside influences.

Probably so. Dukat wanted to be loved (and his daughter DID love him, which may've been a major factor in his decision not to kill her, in addition to the fact that Kira was watching and might feel honor bound to kill him in turn), but he didn't want to have to put himself out at all in order to gain that love, so there was a focus on the surface of things.

Damar, meanwhile, starts out as Dukat's loyal shadow, and then reluctantly fills his shoes after Zial's death (at his hands) sends Dukat off the deep end. Perhaps his ability to feel guilt over that (over what it did to Dukat, rather than over Zial's death) laid the groundwork for him to eventually 'get it' when Kira points out that the grief and outrage he feels over the Dominion killing HIS family is no different than what too many Bajorans had experienced at the Cardassians' hands. Damar learns, eventually, to empathize with someone outside his own circle and species.