Originally Posted by Ensign

There are actually some pretty good reasons why this idea fails spectacularly. The main one is that it completely overlooks why really degenerate builds are run in the first place. The builds are not broken because they contain 6,7, or even 8 of the same class or character. They contain 6, 7, or even 8 copies of the same character because something about that character is overpowered. Those builds tend to find a broken mechanic and stuff as much of it into a single build as possible. Hence the degenerate class lists aren't the cause of any sort of problem - they are a symptom. Those problems do not go away if you put another rule in place to restrict the expression of a symptom.

One of the interesting consequences of these builds, if you follow them closely, is that only rarely is the thing they're exploiting so good that it's worth giving up all the utility that you lose by running those degenerate characters. IWAY was a great example of this - starting as 8 Warriors, it quickly turned into 7 Warriors plus a Necro, then 6 Warriors and a Necro. Later, it dropped even more Warriors for Rangers with traps and spirits, falling into a stable 4/2/2 for a long time, before it began to evolve even further - later versions even included things like Fire Eles. Paraway eventually started to notice that extra Paragons were useless and those started to turn into Warriors and Rangers. Bloodspike added a dedicated Monk and Ritualists over time. Unless something is really broken, it starts to balance out as the new concepts its exploiting tend to solidify and become adjusted to in the metagame.

There has been one exception to this rule to the best of my knowledge - Searing Flames. Searing Flames was a skill designed to have a ton of synergy with itself, and it does. A single copy on its own is fairly weak, however as you added more and more copies of the skill it began to break messily, each added copy being better than the last. Searing Flames started to break, conveniently, when you ran 3 copies. More copies continued to get better, but the loss of utility began to catch up after a point - teams dropped from 6 to 5, to 4 or even 3 copies of Searing Flames in serious Searing Flames builds in order to shore up its weaknesses. 3 might have been the optimal number of Searing Flames Eles to run on a SF team right before its nerf.

So it should be easy to see why this sort of restriction would be bad for the game. It doesn't fundamentally fix any of the problems that are breaking the game - those would exist, and need to be fixed, with or without the cap. It would, at best, moderate the effects of broken skills and mechanics until they could be fixed properly. On the flip side, it puts another non-intuitive rule into the party formation process, eliminating harmless builds and stifling the process responsible for a lot of advances in our understanding of Guild Wars and builds, those all-in, one trick builds that eventually evolve and have parts copied by the game as a whole. When the only benefit is 'it makes our big mistakes look better', there really isn't much to discuss - this sort of rule would be a big loss to the game without any appreciable benefit long term. Why it keeps being suggested, I don't know.