That's one of the reason I loved Eureka. You could play any job you want in any role you want, and you'd always find a party.
Or, something I suggested several times in the heated debate about BLU, is for each job to have its core for matchmaking, but have customization as a limited feature for when you play solo, unsynced or in full premades.
You wouldn't have that problem with content of larger scale. People don't really notice if an alliance is not 100% following the meta while they do for a party, even outside of Savage. The more people you gather, the less people will expect to match the optimum setup, especially if you can't create the whole group outside of the instance.
