I really think what made her work was her team. Other than Roserade and Gastrodon, her Pokemon either came from plot eggs(meaning she's as important as you), unique encounters you probably didn't find the first time round (Meaning that she knows more about Sinnoh than you) or are from locations tucked in a corner. It helps to make her feel like a representative of the best parts of the region.

You'll find 5/6's of Alder's team just walking around in the grass, and while Iris has a decent team, 2 of them are from previous generations, Denio and Drudd are common encounters , Milstralton Cave is practically begging you to explore it, and the route from Relic Castle to Nacrene takes no effort. It doesn't feel as imposing as Cynthia.