Rank the classes.

[Karthil]

I think you've gotten a lot of info I'd agree with, with a few caveats:

There are classes that are very sought after for grouping, but most groups usually only want one of them: Cleric, SK, Pally, Ench.

Sure, you'll get flexible people who have 2 clerics in one group, and I'm by no means suggesting that there should ONLY be one of each of these per group, but people do tend to think of groups that way. So even if I'd give each of them a 10 for grouping, they tend to be a one-and-done type situation.

Then you have rogues, warriors and monks. Because melee DPS is never redundant a group can easily have any number of these classes (once you have at least a healer, maybe cc, and in the case of the rogue, a tank). I would say that these classes in and of themselves might not get a 10 as easily as the previous classes (maybe an 8 or 9?) but because there can be multiples of each class in a group much more effectively, I'd actually rate them a 10.

Just my thoughts :P