Well this will be my first post I believe, and normally wouldn't write one, but then again, this is afterall a very important subject to FFxiv's future.

First things first is the problem of the low level of dedication needed to play eny of the current jobs well, and become extremely well geared without having to play the class you are gearing up for at all. With that in mind lets look to where the problem originates, compare alittle to ffxi as I am an old player, and then find a solution.

Origin and comparesing: In ffxi you had to be very good at your job to get enywhere as it was all teambased which was taken out of FFxiv to make it less time consumable which was very much needed, but because of this change the game became alittle easier and the pride one got from it was lowered.
Next was the job system changes with a view from reallife I imagine changing ones job with the switch of a weapon, since in reallife if you use a pitchfork you will be considered a farmer, and if you then change into a suit with pistols starting to kill people you will be something else. This means the old job system was "flawed" and this new one is by definition "better" or closer to the truth of life whichever way you want to look at it. The problem created with this change though was the drops you got from one job could be used by the other which meant the leveling was further lowered in difficulty and people having good gear didn't have to get it from using that job at all so things like uniqueness and comparing gear or abilities died off again lowering the pride one should have.

Solution: Now the first problem FFxiv got rid of as best they could by making mobs call for others to help them if you were in a party. It made it harder and was still rewarding as you had an easier time getting the exp chains so I wont really go into that one as its more tweaking how much it should be better or worse and if the harder mobs like bosses should get trash mobs with them if a party escalates from a half to full and so on and so forth.
The next problem however giving people grieve in this post is mostly the issue of gear as there should always be a fair decree change in gear between dedicated and parttimers. The only real way I see this change in a somewhat reasonable fashion all can agree on to a certain extent will be in two parts. First by having the endgame bosses only drop to your current job, because if you do it with lesser mobs people will complain, and in that way you will still be able see a real difference in peoples gear compared to what they are good at since no party wants a poor healer and so on just because they still need that gear. The next way is to use a "skill evaluation quest" from time to time like in you got in FFxi at last levels. Simply put make a quest line for each thing needed for that job, like with healing a npc party in a fight so noone dies and with the higher the level the more difficult it will become by having the healer to dispel and parhaps even raise at the same time. This could be done around every 10and give a really good item to use for the next ten levels or so tillthe next part of the chain comes up and again at max level.