The best element for overdrive stalling by far would be water IMO. You have Ryu-Oh for overdrive extension, which means you can free up an ex slot/ don't have to rely on Mordred, you have both Cthulhu and Snow Raphy for orb removal, and the girls work pretty dang well together (Any soul Ryu Cthulhu and Raphy or Mordred/ Ex BB Cthulhu Raphy).
And if you want to go Full Retard(tm) on the orb removal thing, Water also offers Dagon. R with the orb removal.
And allow me to note Mordred's debuff- and a Ryu-Oh with 6% Affliction does not give Ryu-Oh 100% success chance with her Black Propaganda (against neutral). It is high, but not 100%. Just something to keep in mind.