What?

Contagion takes nothing from you and can be used while you're doing anything. The only reason I can think of to delay contagion is so that you get a tiny bit extra dps from your pet during Spur/Rouse so it doesn't have to do the contagion animation (which btw, I'm not sure if it even actually delays wind blade since that has a CD).

Using energy drain during RS is a dps loss any way you look at it, starting around 20 seconds after opener when you could've gotten a third Fester.

RS is nice but its not the greatest thing ever. Its not worth sacrificing anything to put more stuff into it.