Sweet baby jeebus, this part is so true. Since Wrath was brought up in the OP, I'll use a Wrath example of this:
2nd ICC 5-man, Pit of Saron. Just after the Ick/Krick, where you have the few seconds to zerg up the ramp before the two groups of trash form up, those two possibly presenting the hardest pull in the entire instance.
So many people wanted to skip it than do it when my wife and I would PuG it as tank/healer. Now, I didn't really care either way philosophically, but someone would invariably either not make it, so then the party was split between both packs, or they would pull one (or both) trying to make it up the ramp too slowly.
So it got to the point that we would just sit at the bottom of the ramp to avoid the inevitable wipe and just do the two pulls like normal.