A suggestion for reward balancing in AE missions

That kind of abuse is probably addressed by having a hard limit on how many times an account can register a challenge score each 24 hours.

You are not thinking like a Min-Maxer and this is leading you to the same problem the Devs face. Add a rule to stop an exploit and the Min Maxer finds a new exploit. Add a rule to stop the new exploit and the min maxer may well find a way to use your new rule to add an even bigger exploit.


In this case you have decided to limit it to 1 defeat per 24 hours.

The Farmers will thank you since The Power Level Set will have almost constant deaths and reward more while the Non PL sets which are played less and when played have fewer deaths will reward even less. The reason for this is as follows.

The farmers simply do their war cry of "AE PL FARM!!!" to assemble thousands of players and has them all die at the start of the first run every day. Now the PLPowerset is ranked +8 in difficulty for every team of Power Levelers and quickly becomes the most difficult set in the game with Max rewards.

Meanwhile the Non-PL sets outnumber the PL Powersets and so will not be played as often resulting in a low difficulty score.

Even worse when they are run the NonPLpowersets will be run by normal players fighting to live and so on most runs the Power Sets will score no difficulty points since most people who play them won't die resulting in an even lower number of points.

End result is that the tougher power sets will reward less then they do now, and the PL power sets reward more.

Good point there. Yes, my original suggestion would yield a gross advantage to popular sets, regardless if they are popular for PL reasons, or just because they are on top of the selection list or appeal to a current trend. Worse indeed would be that rarely played powersets would yield far too little.
But this might be solved by having the challenge score divided by the cumulated number of defeated enemies, aka a case fatality rate. It's like how doctors estimate how "challenging" a disease if for an individual.
Note: the number of defeated enemies can't be lower than an arbitrary number (relatively low) in order to prevent divisions by zero.

CLARIFICATION
Sorry if I am misunderstanding you as I am unclear as to how the "challenge score" is now figured. If I am understanding you you are proposing that only a certain number of defeats per account will be counted towards the challenge score, and that those defeats would be divided by the number of enemies killed by that account in the same period. In other words now the PSDS (Power Set Difficulty Score) is a Player Deaths/Kills with a cap after X number of deaths.


FARMERS CAN STILL FEED THE SYSTEM FALSE DATA
The Farmers will simply die a few more times to up the PSDS. Bare in mind that Farmers have been using teammate deaths to boost their farming speed for the last 8 years by using Vengence, Rise of the Pheonix, Self destruct? and other Death based buffs and damage powers. Level 0-10 and 50 chars can in fact enter with rez inspirations and suicide multiple times to hit their Powerset Death Cap with little or no effect on their farming.

The farmers will still cause an "easy" Power Sets to get a high PSDS ranking, while as I pointed out previously the normal power sets will get a low ranking in comparison.


CODING, COST AND RESOURCES INCREASE
Further more your code is increasing in complexity and requires more system resources, as well as time, money to develop, code, and test. Standard Code Rant of course applies but we are probably looking at something like this.

Your first proposal required tracking a players account and upon death making a note of what killed them. This process only needs to run when the player dies so only uses system resources ~0-5 times per mission.

Now your code has grown to the point where whenever the player kills an enemy the system must increment the "Power Set Mob Death Counter." This process will need to execute hundreds of times per mission in the middle of combat thus adding more load to the system during a time when the system is quite busy.


YOU ALWAYS HURT THE ONES YOU LOVE.
Even if you are somehow able to make this system work it will most likely hurt the non farmer (Story Teller and Story Player) far more then the Farmer. Farmers often use custom character builds combined with story designs and enemy Power Sets. Often these Missions and Power Sets are difficult or impossible for your average character and player to run. Should you succeed this will result in Power Sets that are difficult for the average player being ranked easy and giving less XP thus hurting those who run the stories and those who tell them. And in the end the Farmer will move on to the next easiest power set FOR THE FARMER.

You can see this with all the nerfs to date. Many features have been reduced in rewards and therefore effectively removed from the AE Story tellers pallet, without seriously impacting farmers. The latest is the "Ambush Nerf" which has eliminated the classic comic storytelling device of swarming the hero. I used it in my HP Lovecraft inspired story to allow the NPC Deep Ones to swarm through the streets hunting down the characters. The Farmers have simply adapted by switching maps, adding patrols, and advancing into the next mob.


IN THE FUTURE DO IT FROM THE GROUND UP
I don't think fighting your average Farmer, MinMaxer or PLer is worth the Devs time and effort, but IF they are going to do so they must do so before they design any game add ons AND listen to those players who spend time testing stuff. Programmers know that it's far easier to fix a problem during development or testing phase then after the system has been released. Game master know you will hear far less complaints if you start a game with a rule that prevents players from abusing a system then if you try to add one later.

Hopefully the Devs have learned these lessons and future content as well as player enjoyment will not need to be butchered in order to fight PLing.