The obvious answer is no. This is my process
Mash at X temp for Y minutes
Drain wort into kettle
Add sparge water to tun and mix
Drain wort into kettle.
I ask because this is how i thought it was done but according to John Palmer when you mash, before you drain any wort, you add your sparge water then drain.
As for efficiency, I am usually 70-80 with my current method.