The party cap isn't necessarily a bad thing.
The current system is flawed, and they need to fix it. Obviously, having fifteen people in a "party" is a bit excessive. If the game is going to get better, we need to have smaller groups that can work together in a unified party, where each person has a role, and fulfills their role to the extent of their abilities. With fifteen people, we'd only need a tank, a good healer or two, and a bunch of idiots that can hit the "1 key to rule them all." There is very little skill in the game, and by reducing the amount of people we can have in an average group, they lay down the foundation that groups are supposed to be dynamic, and that party members are supposed to cooperate to get the best out of their group.
For end-game content, (that is not currently present in the game), I do agree that we will need Alliances. I would like to say that I doubt SE would over-look this feature, but hey... look at the bloody thing. If SE didn't over-look things, then we wouldn't be posting here. We'd all be playing a fun, interactive, and engaging game.
I'm not sure that I like the 4-8 system. It seems strange to me that they wouldn't stick with one number for groups, and then make an alliance as three of those groups. I think the ambiguity comes from the fact that we have a "small group" and a "big group." As we tend to think of Parties as the "small group" and Alliances as the "big group." But I think that when content is released, SE will do a fair job of making it accessible to everyone who is appropriately leveled. (Side rant: put a level requirement on Behest, so we don't have ****-wads purposely gimping SP).
As far as the problem of elitism....
It happens in every game. Some classes will be better at certain things than other classes. There will always be classes that are more desirable than others. In every MMO that I've ever played, (going back to EQ and EQ2), there have always been more people interested in blowing things up like an r-tard, rather than working as a team unit, like a tank/healer combo. Elitism is a good thing in these kinds of games. It keeps little kids from wasting everyone's time in an end-game encounter.
For example: one of the main complaints about the job-overhaul has been from Conjurers freaking out that they won't be able to be a DD class with the ability to heal itself. Some of them think that splitting the class into Black Mage and White Mage would be horrible, because then they'd have to choose a role. They liked the idea that they could look for parties as a Conjurer, (to which most people would say that if you can heal/tank, then you are a healer/tank), and then they say, "Oh, I just want to nuke. lol." (I see this way too much, even in my own LS. And to these people: You're doing it wrong!)
As a player of FFXI, I completely understand the concern that leveling some jobs will be useless, like Pup, or Drg, or Bst... There were times when I was leveling my mage classes that I saw these poor melee-DD's LFG for hours on end, and I felt bad for them. We always picked the ones that we thought would do the best damage, and I hoped that the others would take the initiative to group together and find a healer and tank. In end game, I felt bad for players who had only leveled certain jobs that others could out-perform. It sucked. But, generally speaking, the player will be the most important factor in who gets into a group.
Let's face it. If you've ever played FFXI, and ever had the misfortune of bumping into that 0.05% of the player base that were just complete ****-bags, then you know that no matter how much damage they do, you'd always pick someone, anyone else to be in the group. Names of bad players would echo through the player base. I remember specifically watching people leave group when they saw a notorious player, or would /tell me, (I generally made my own groups), that we needed to watch out for some ****-bag that would roll lots on every item to drop, like we were still in the **** Dunes.
This is also true for good players. People who are polite and pleasant would always be remembered. If I ever saw another player that impressed me, either through their efficiency, or just over-all fun personality, I'd add them to my friends list. The next time I was building a party, I'd check to see if they were on and if they wanted to come with me. It doesn't matter what job they played, as long as they were good at it, and they were nice people.
I think the only reason anyone should be worried about elitism is if they either want to half-*** their job, or if they think that they don't bring anything to the team, and that someone could easily replace them. And for people like that, they need to figure out why they don't bring anything to the team. For me, personally, I tend to be a support character most of the time. As a player, I try to be patient, and I try to help my team mates when they are confused. I also try to be a little social, and bring some fun into the party while we're all grinding. (Though it is hard as **** to write and battle at the same time. They can't put in chat tabs, like XI? Really?)
Now, I also understand the problem that some jobs are specifically better in certain situations, and I'd like to say that this could be balanced. (I'm thinking of Summoners in CoP). Unfortunately, that probably isn't going to change. It's SE after all. There will always be an optimal job selection. But I don't think that SE is quite the one that dictates what job is better in those situations. I think they just make a scenario that is supposed to be group content, and the player-base has a few "go-to's," like /nin, or Astral Flow. We're given a puzzle, and told to figure it out. As players, we tend to have a few favorite tools that we go to, and figure out how to make them work. For many encounters /nin isn't really necessary. But we do it as a safety precaution, and to keep the healer from actually having to do much of anything, so they can focus more on status ailments.
So how do we fix this? Obviously, 80% of the population is going to go out and role a damage-dealing class. The other 20% will have their pick of who to bring along for groups. It's a social game. So mingle. But for those anti-social people who are too damned lazy to start their own party... you can solo. That's the one redeeming factor about this game over FFXI, (before they nerfed the whole game). Back in the day, a DD had to advertise why they should be chosen over their competitors, or they'd have to wait for there to be no competition, (generally because they got invited to other parties). But now, if you have gimp gear, or don't want to use foods, or you can't stay for a full EXP party, or maybe you're just a jerk and no one wants to play with you anyway... now you can go play by yourself. It's great.
As for end-game content, I'm sure that initially, all the classes in the game, (I'm not referring to crafters, as I still refuse to acknowledge a crafter as a legitimate class), will be welcomed to a party. We currently have a very limited amount of classes, and as of now, they're all the same anyway. Once the classes are unique, and we get some more classes, then we'll be able to figure out what works better than what. But for now, the game is so messed up that we don't really need to even worry about this. Just pick a few friends that you like to play with, and go have fun until your EXP numbers turn yellow. Then curse, swear, log out, and wait a week or so.
So yes, the group system is a good thing, I think. Having fifteen people just throw themselves at the mob is a bit Levée en masse, don't you think?
But I would like to see an Alliance system, once content is introduced that would permit such a system.