Now that we can agree on.

Roby does not dominate a tackle on his own, he like Houghton is a good defender and very similar in that he is quick and the first man in. To turn a player on his back is to totally dominate a tackle and very few players in SL can achieve this on a regular basis alone and the ones who do are usually big powerful props. Houghton does what all hookers do and most h/backs they make a tackle, to totally dominate generally takes 2 players. My views are not simplistic the stats don't lie, now if you want to discuss which players in the league are the most effective at dominating tackles on a 1 to 1 basis that is a whole different discussion, however what I will say on that it certainly not hookers and half backs who will be any where near the top of that list, it will be props and big forwards.
I agree that Houghton will benefit from Hereimia and it will hopefully develop his game futher

I've seen Roby dominate plenty of tackles, he has a fantastic tackle technique. Your views are very simplistic, by claiming a low missed tackle count makes Houghton one of the best (you initially claimed THE best) defenders in SL just proves it. You've said yourself that he always needs the help of others to complete an effective tackle so how on earth does that make him one of the best? Perhaps you meant one of the best relative to his size? Were all guilty of looking at our own players through Rose tinted glasses at times but Houghton is currently nothing more than a decent standard SL hooker. He is still relatively young and may well go on to become a very good SL hooker (let's hope so) but talk of him being International Class is well wide of the mark IMO.

Robys only missed 9 this year (out of 573)

Houghtons missed 22 out of 714

and for balance Mcillorums missed 35 out of 539

Mind you if its going on percentages then Logan Tomkins must be one, if not the best hooker , not missed a tackle yet

I'll answer that if you can tell me what constitutes a missed tackle in the stats.

The aim of any tackle be it dominant or not is to stop the offensive player, thus forcing a play the ball. Hougton is presently the most effective player in the league at this there is nothing simplistic about that, the tackle is either made or it is not and the offensive player carries on until effectively the tackle is made. We will agree to disagree about Roby as no way does Roby consistently turn a man on his back on his own, very few players in SL do that alone, Roby like most hookers/h/backs rely on the 2nd man coming in.

I suspect where the player grabs but does not force the ball carrying arm on the floor or the ref to calls tackled if he is satisfied that the player is stopped.

No he isn't!

So we've gone from the best defender in SL to one of the best to the most effective at making a tackle with the help of others whether or not it leads to a quick PTB or not. Brilliant!

Not sure where this concept that the opposing player needs to be put onto his back in order to dominate a tackle comes from either. A lot of it comes down to the collision, an area Roby does well in. Houghton, however, doesn't fare well at all and usually loses the collision. Players constantly go over the top of him and find the ground quickly, winning a quick PTB due to dominating him in the tackle.