One of the things that really handicapped some of the experiences in FFXI were the uses of some jobs in different battles. I'm not specifically referring to leveling, in fact most of the problems occurred during missions. When CoP came out the term "Cookie Cutter Party" started becoming associated with pretty much anything involving fighting in the game, and it was way overused for it be considered anything other then a problem. Sometimes it was unfair (manaburn paries), but a lot of times it was a necessity to get things done with a standard party, and people took crap for it. There were many times when I was creating a group for a CoP mission and shouting in Jeuno or Whitegate, and someone would say he needed the mission. Unfortunately if that person wasn't one of the jobs needed for the mission I had to straight up deny them. Obviously it is possible to beat these missions with any job, but I'm not wasting 3 hours bringing a Beastmaster to the airship battle just to "attempt" to beat the mission and make him happy. I am going to make the best party possible, and I don't think SE gave us a lot of wiggle room when it came to this. I'm sure I have been lied to about a party being full because my job didn't fit for the mission or party and of course I am angry about it at the time, but I totally know where the group leader came from.
No matter how casual FFXIV will be, we all know there will be missions that take hours to complete, and a person shouldn't feel a burden because they want to make the best party, or because they are dragging the group down due to their own satisfaction. I'm sure a lot of people had a job like Dragoon leveled when CoP came out, and they were forced to either level a new job or wait days for a group nice enough to take a risk bringing a weaker job to the battlefield. Hopefully the fighting in FFXIV will make it so skill is much more valuable to a battle then job or equipment. That way the battles will be just as difficult, but everyone has the equal probability to win the battle no matter the job.