I was recently reading the official eq2 forums about class balancing, and the upcoming combat restructuring to be (in descending order of highest DPS), mage < scout < fighter < priest. A lot of interesting, and not so interesting rhetoric was slewn about, mostly with regard to how the fighter DPS classes will fair after the changes arrive (beserker; bruiser).
Among the discussions were viable roles for classes within a group situation. It was the standard, TANK, HEALER, DPSx4. The tanking ability, or skill set, is not stackable; offtanking is a rare occurance, and therefore, groups are not built around needing more than one tank. Likewise, one healer is usually enough to get the job done, for any given encounter (non raid/epic). But yet, there is an equal selection of classes, archetypes and professions to choose from. Let's cite the law of large numbers and assume that there is an equal representation among all classes. After combat restructuring, if it indeed places fighters behind scouts, then the six person group will be less likely to pick a 2nd (much less a third) fighter to fill the remaining spots: assuming a group of, mage, scout, fighter, priest. So this leads into the classic EQ1 examples of economizing group mixture to obtain maximum balance and efficiency. Therefore, the two open spots in our hypothetical group, would likely be filled with either scout/mage, scout/scout, or mage/mage with emphasis placed on a different archetype or subarchetype to avoid spell stacking issues and allow for greater utility.
This is all nice, and none of this is new. The new part, is simply what the title suggests: "What could have been." This means that, for a given group with six spots to fill, and presuming that groups will economize such that only one tank and one healer will be desired in a group, class variety should reflect this. There should be a mechanic in the game that limits the variety on classes, such that if each class were represented equally at all times from a mass population, then supply would equal demand, more often than not. By equal representation, I'm saying that for every four new characters created, there are four different classes being played.
If EQ2 had six distinguishable classes to choose from, at character creation, where one is a tank; one is a healer; and the remaining four are DPS in some manifestation, then at any given time during play, there will be "just enough" or "barely not enough" of any given class. Rather than, a ton of fighters LFG or a ton of healers LFG. By removing the flood of same-classed characters from the LFG "pool", they stop being a commodity and become a luxury for when the do go LFG.