The sin bin was designed to punish repeat offenders or for cynical acts. It was never designed to be used for foul play.
They got rid of having a 5 minute or 10 minute sin bin as the media, amongst others, complained there was too much inconsistency in relation to what for one referee would see someone binned for 5 minutes would see a similar offender given the bin for 10 minutes.
Now problem has been, mainly due to media pressure, referees became gun shy to send players off as too many in the media would go on about how it robbed the game of its competitiveness. In fact by the 1990s, this is where the "put them on report" vogue came into the equation. It was the same media pressure about "the team subjected to foul player getting no reward" argument pushed by the media that lead to players being binned in the first place.
On stuff like this, the ARLC need to stop being so reactive to the media, and stand by their officials. Yes mistakes happen, but until we all stop this endless b/s about "referee x cost us the game" mentality that prevails in rugby league, this will just go around in circles in my opinion without any real change happening.
I mean in the late 1970s-early 1980s rugby league saw a lot of foul play on the field. High tackles, biting, punching, kicking, elbows to the head. They only got rid of it by referees sending players off and the judiciary coming down hard on them if found guilty when handing out sentences. With the kid glove treatment handed out today in comparison, its no wonder things have remained the same.