The players know this, but I am not sure Venan does. The weekly Hero Score contest has largely become "who can hit the most KFS raids in a week" as KFS has the highest hero score results of any raid by far.
This sucks but at least it is a level playing field. The upcoming update increases the max level to 45. At 45, you will get hero score for killing levels 31 and up. All phases of KFS are level 30. This means that players level 44 and below can still milk it and level 45 can't.
There are a couple of huge problems. First, it is unfair to level 45 players. Second, it creates a reason for people to avoid leveling.
My ideal solution is to prorate the HS based on the level difference between the player and the monster. Sure you could just adjust the limit again and leave the HS numbers flat but you've tried to this a few times and there is no sweet spot of solving all the issues that have been raised.
I would not worry about this killing KFS. KFS will live on for silver reasons, it is a great raid that is finishable with a moderate amount of effort, and that the OS phases are fun.