If you want to stop gang tackling, then start rewarding one on one tackling. A couple easy changes:
1) Any one on one tackle means the tackled player cannot play the ball until the tackler is square at marker, signified by a call of "play it" by the ref when the marker is ready
2) Any 2 person group tackle initiated around the legs WITHOUT lifting e.g. one low, then one high. Shall be deemed a dominant tackle and the tacklers will be given additional time to hold down
3) As soon as forward progress is halted, held is called. Additional time allowed for tacklers to get back to marker
Seriously all this wrestling nonsense only came about when the rules were changed to punish text book tackling styles in an effort to artificially speed up the play the ball. Once players started getting pinged for holding onto the legs and holding down, coaches had to develop wrestling techniques to hold up the player, extend the tackle, and give their side a chance to get back onside again.
Remove all the stupid "holding down" and "MOOOOOOVE" calls from the game and wrestling suddenly becomes redundant.