As someone who watched him all through his Tigers years, you are totally correct that he was hard to get to the ground, hard to get on his back etc....but....this is the problem.
He hits the line like a pillow, usually backwards and then YES he is hard to get to the ground, has great wrestle defences. Trouble is the whole "No, you arent taking me down and Ill fight the wrestle" thing takes twice as long as being tackled on your back and playing the ball. IMO Defences worked him out, stood him up and let him have a long drawn out "win". He is never going to hurt anyone, break a tackle or give an offload so as soon as he engages two defenders, the defensive line turn their back and jog back into position in the 17minutes it takes Woods to stop his judo lesson and play the ball.