I think this is on to something. I'm on PS3. To test it out, so far I've played three games with these checking/hitting sliders:
Hitting Assistance: Maxed
Aggression Human: Maxed
Aggression CPU: Empty
Hitting Power Human: Maxed
Hitting Power CPU: Empty
My hits, when I could line them up, would be the ones you see people complaining about; I would bounce off of the opposing player. Every once in a while, we would bounce off of each other. Usually, the opposing player kept possession of the puck. The ice diagram that you can look at between periods rarely showed any hits, and those hits that were shown had no replay available.
Then, for one game (so far), I maxed out Hitting Power CPU and emptied Hitting Power Human (everything else remained the same). When I could line up a hit, I put a good hit on the opposing player. If they had the puck, they always lost it. My player stood his ground while the opposing player usually found his backside on the ice. For the first time in NHL 13, I injured an opposing player with a hit and not a slapshot. There were at least 5 hits indicated on the ice diagram between periods, and the third had 10, many of which had replays available. Some hits I don't remember delivering, so I'm guessing that the slider also affects my CPU teammates as it does me (which would make sense, it was that way in the past, right?).
Now, I'll concede that these sliders are exaggerations (for lack of a better word) of what I would normally play with, but I wanted to test with these things completely in my favor and swing it the other way to try and get what I would consider baseline information--best and worst case scenarios, if you will.
All of these games have been Tampa Bay (me) at Montreal with 8 minute periods. I'll try some more games, same teams, same settings as the fourth game, to see if the hits are consistently better than the first three games, but I have a feeling they will be, so long as I can line up the hit.