That's not exactly true Bagstone. The topic maker asked for the fastest T13 Class/build. The correct answer for that is Necromancer Singularity Speed.
What makes the Necro faster than the wiz comes from all the damage is passive, you will never have to stop to target anything, you just blodrush forward while your 10 Skeletal mages shreds everything on the way all trash, every pack dies instant. No targetting required, no stopping, no clicking. no nothing. From you kill the elite pack to the boss lies dead takes consistently 2 mins on GR70. That speed no other class can pull off.
Once your hitting the GR80, yes the roles switch and wizards are consistently faster. But that was not the question.