There is a difference in the NFL though, the NFL knew that concussions were causing long term damage to the brain and actively told players that this wasn't the case. They misled players and that is why they are being sued. The NRL has not misled players and could have notified players that the research shows that concussions cause long term effects and put in strict protocols on concussion testing. There is a reason boxing and UFC still exist as a sport and the aim of those sports is to knock your opponent unconscious.
The NFL has not banned shoulder charges, has not banned contact to the head. They have banned helmet to helmet contact and restricted hits on defenseless players and brought in strict concussion protocols.
The misdirection is part of the NFL situation, but there's a duty of care issue as well.
No the NFL was sued and reached a settlement over the concealing of information relating to the long term damage concussions cause and that they returned players to the field too soon despite this knowledge. They were not sued because of concussions occurring in the sport. They were sued primarily because they lied.
PHILADELPHIA – The NFL has reached a tentative $765 million settlement over concussion-related brain injuries among its 18,000 retired players, agreeing to compensate victims, pay for medical exams and underwrite research.
A federal judge announced the agreement Thursday after months of court-ordered mediation. It came just days before the start of the 2013 season.
More than 4,500 former athletes -- some suffering from dementia, depression or Alzheimer's that they blamed on blows to the head -- had sued the league, accusing it of concealing the dangers of concussions and rushing injured players back onto the field while glorifying and profiting from the kind of bone-jarring hits that make for spectacular highlight-reel footage
http://www.nfl.com/news/story/0ap1000000235494/article/nfl-explayers-agree-to-765m-settlement-in-concussions-suit
Though after looking into this there are a couple of lawsuit that have recently been launched that state that players were coached to lead with there head when tackling in 70's and 80's. So this does support your argument. This is likely to be unsuccessful as the previous settlement is supposed to include all players who retired before 2014.