A lot of the normal tackling (square) is big hits that drive you back. I believe this needs to be toned down a bit otherwise there's no need to be risking the big hit (triangle).
Majority of the normal tackling should allow attacking team forward momentum and quick recycle of ball.
The big hit (triangle) should be based on timing, a poorly timed tackle results in high tackle etc, whilst a well time tackle results in knocking the ball out or driving attacking player back allowing you to win the ruck.