Gearscore doesn't measure skill. Damage meters measure damage or healing, but can't say whether that damage or healing was put on the right target. And threat meters only show the situation right now, without a history. As everybody knows that the most important thing after a wipe is to attribute blame, the previously existing addons were obviously not sufficient. Enough of that! Now the same team that developed FailBot developed Blame Meter, the ultimate addon to correctly attribute blame *after* the wipe.
Blame Meter measures damage and threat at the same time, and thus is able to determine whether you either did not do enough damage, or whether you overaggroed the wrong target. It also measures healing while simultaneously checking which target you *should* have healed, thus giving out a score based on how much healing you did to the right target, with negative scores for letting people die. And for the tank it determines how well he held aggro, as well as how well he mitigated incoming damage. At the end of the fight every participant in the group or raid has a positive or negative blame score, with the player with the highest negative score being the one who is most to blame.
Forget about all those other addons, Blame Meter is the last judgmental addon you'll ever need. Blame scores are sent and saved to a server, where other players can look at them. Thus for organizing a pickup raid it is obviously much better to check Blame Meter score, which includes both gear and performance, than just check Gearscore, or easily faked achievements.
Recently some blogs have discussed the changes to responsability that Cataclysm will bring, with Greedy Goblin Gevlon thinking that DPS will have no responsability, and Troll Racials are Overpowered Klepsacovic thinks that this is a good idea, because "the majority of players are somewhat lazy and uncaring", and only the minority of responsible players should play healers and tanks. There is an endless fight going on for years in which the healers and tanks blame the dps, while the dps blame the healer or tank. Blame Meter ends that discussion by clearly showing to everybody who is to blame.
The only problem with Blame Meter is parametrization, which is heatedly disputed on the Blame Meter forums. As the addon measures different things and converts it into one single blame score, it must apply statistical weight parameters to everything it sees. How many negative blame points is standing in the fire worth, and how many of those do you put on the priest for not healing him, or in Cataclysm for not pulling the player out of it? If a dps overaggroes, how many blame points does the dps player get, and how many go to the tank for not holding aggro better? After it was discovered that one of the addon writers plays healer, accusations flew on him having unfairly put too low blame weight on healer faults. This is why currently Blame Meter has been removed from all addon download sites, until the correct parameters can be determined. Hold your breath, that can't take too long. Or can it?