This, I was pretty upset with some of the people in my guild for not learning it, then we had a run 3 weeks ago and we got the 25man safety dance achievement, so I think I jumped the gun a bit on labeling the people who struggled with it. But Heigan makes up for that by being able to be pretty much 5 manned. If you have 2 healers, a tank and a 2 dps that know the encounter like the back of their hands and never so much as get hit by a splash EVER let alone killed then you can essentially carry the other 20 people to free loot and badges.
Thats how we killed heigan 25 in our first few runs, Im not ashamed to admit (probably because I was one of the five, but whatever). Heigan (ed: Thaddius) on the other hand we just had to bang away at until people stopped missing the god damned jump. They slapped all of us hunters in 4 different groups (we are a hunter heavy guild) and stuck people who had trouble with the jump in our groups for aspect of the pack, and thats how we got Thadd25 down our first time. We have all learned it now though.