He's played well over 300 games in 15 seasons and been part of 3 premiership teams. Must have been doing something right all these years. I've never regarded him a "ducker" as such, he developed this style of warding off the tackle with his arm resulting in many free kicks for high contact. Whether it's illegal, the umpires don't appear to think so. Neither do I. For years I've claimed many players don't go in low enough with the tackle.
He gets the trainers to squirt oil from a sauce bottle at every break so he can do his arm lifting routine.
It is deliberate, it is practised, it is cheating.
The AFL should have dealt with it a long time ago.