I love how people complain about addons that rate players based on certain criteria, and then come up with another addon that continues the cycle...
This was only a suggestion and I was trying to throw some ideas around to help the general community which is what I believe the suggestion forums are intended for. However good or bad the idea maybe, constructive criticism is always helpful. Unfortunately in the internet community there will always be trolls like yourself.
Rather than write a bunch of logic that tries to assess player skill, why not use one of the many "player rating" addons already out there? If you notice that someone is consistently playing well -- following directions, not standing in fire, doing decent damage/healing, has a good attitude -- then give them a positive rating. If you notice that someone consistently ignores directions, stands in fire, deals no more damage than the tanks or heals less than a ret paladin, and/or is a jerk, give them a negative rating. Encourage your friends and guildmates to do the same. A rating that reflects the average of many people's view of a player will probably be more helpful than an addon's attempt at rating a player's skill.
To be honest I didn't know there were addons already written that does this.
In my opinion Achievements and GearScore are not an accurate representation of a player's skill in a raid environment. And a player's skill is what can make or break the raid more often than his gear or achievement. A player could fail at a raid boss encounter and be dead for 90% of the fight and still earn the Achievement when the rest of the raid kills the boss.
I thought of this idea after reading about an addon called EnsidiaFails which from my understanding posts in raid chat when anyone raid member fails at a particular boss tactic. It would not be hard to build a player's own database based on this kind of mod.
I would like to see an addon which could rate a player's skill.
For example, upon installation of the addon you would have a skillscore of 0. Each time you fail at a particular raid boss tactic such as Emalon's Lightning Nova you would lose 1 point. Each time you do not fail at a boss tactic you would gain 1 point.
Another option would be to give the player a percentage score. For example, you have encountered Emalon a total of 9 times and of these you failed at Lightning Nova 4 times. Your score would be 55.56%.
Of course Ligghtning Nova is only just one tactic that Emalon uses and raid bosses have several which you will encounter throughout the fight. So your overall SkillScore for that boss should be calculated as a summary based on how many times you fail or succeed for each tactic.