Grading by outcome in the Judiciary is fine as the defending lawyer could then argue "My client's charge is too heavy as the opposition player was falling as my client struck him so there's some mitigation there."
The other argument - and this happened to Richie Barnett in the early 90s IIRC - could be that the player injured wasn't wearing the appropriate gear, so yes, his jaw breaking in that tackle was always more likely to happen that it should have been. Not my client's fault the other player was a doofus, your honour!
But a referee judging a Report/Sin Bin/Send Off on outcome will be swayed by Oscar-winning-worthy performances of screaming/rolling around agony by the injured player. Which any player would do if it was a GF/Final and if that opposition player got sent off, that would really lighten the load...