Thanks for this, OP. I am getting better at it - just LFR so far - although have trouble with the earthshake one. For the others, it's often easiest to be right next to the boss, in the middle, but this can make getting out in time a challenge.
I've found camera angle helps a lot - I gravitate towards a zoomed out, almost top down angle. This is great for all except for the earthshake one again (there's no blue line and with earthshake, a horizontal perspective is often best, as you can see the foot being raised).
If you don't see any lightning blue slash animations, it is the 360°.
A couple of people have found that mspaint sketch useful.
I have also found that you need a decent amount of run-speed to avoid a frontal attack after the stomp. And, of course, never run across the boss.
I haven't done it for a while, but isn't this picture wrong? Afaik in most of his strikes, if not all, "under him" is always covered. At least with the sideways swings, you need to be through him, not halfway through.
Took me longer to learn than I had wanted (mainly because some tanks just whirl him around strangely since they run and still get hit). Then I got the hang of it, and my UI bugged never giving me the button. Awesome. Yes, logs verified that I didn't get hit.
His strikes at are semi circle of 180. The only one that is 360 is his aoe fart stomp.
As a tank:
See blue slashy thing on his left move to his right hand
See blue slashy thing on his right move to his left hand
See two blue slashy things left and right? go behind him
See no slashy things? move away from him in any direction that takes the least amount of time until you are far enough away.