Though I would say that leadership should increase sexiness. I did some testing and here an example. On a full leader ship built with a total leadership of 78*, Bimbazzy deals as much dmg with her regular attack as song of splendour. I would like to add that her weapon and base attack power suck. Allure and normal teases are weak in comparison. Same for Dancer cait and Quintillius.
It's nothing new that song of splendour is broken AF. If SoS got proper scaling, then there would be no problem with leadership increasing sexiness. This would bring the tease action on par with regular attacks on leadership builds. And powers that depend on sexiness would be on par with spells and weapon powers.
Also spells that deal tease dmg are affected by leadership. Berwyn has one and I think Kyoko has one, too. What could get problematic are the former resolve heal powers. Quintillius can heal about 105 hp with his stance. So these powers might skyrocket, if unchecked. Then again, they could replace the heal spell. Running Quintillus as healer instead of Etheryn or Cait would offer more build variety.
*78 Leader ship: 10 Guld ring + 10 Helm of hereos + 20 Conqueros breastplate + 38 from 19 presence. If you min/max presence you get 81 leadership