There are so many good Dark Miasma powers that it hurts to delay them so long by taking those 5 powers (between Stamina and Leadership). Assuming that you do take Stamina at 20, how many people took the Leadership powers by 30 vs taking more dark powers (like Shadowfall, Howling Twilight or Fearsome Stare)?
For a respec (at level 23), I'm thinking of delaying Leadership until the 30s in favor of Shadowfall and Fearsome Stare. (I currently run Shadowfall constantly and find it very helpful.)