Plus, Dukat was proved to be the Prefect of Bajor for a LONG time before the pilot. This was established as early as season 2's "CARDASSIANS", so definitely not Kira's age.
Sorry for not matricuously following the story details when I was 12 and was catching random episodes on network TV Plus its not like Trek doesn't have aliens that age slower than others...
Rene Aunerjonois was one of those actors who looked 50 when he was 25. Like John Hurt. Weatherbeaten.
Patrick Stewart - on the other hand - is very much not craggy in appearance, but his looks were locked in place for almost three decades.