i will be blunt, even if you play with your friend, when you do the main quest, you do it alone, even if they are here, it's a solo experience. we love or hate it, but that the point.
if you join a game for play with friend, if they help you to do dungeon, isn't playing with them?
level up one jobs to max level is not even that long now, get 60 is a matter of a few day with deep dungeon, behind you will need to do every quest, but if you equip yourself, with crafted gear, or simply by doing deep dungeon as 60 you can get nice gear and the dungeon below a certain level can be simply rush in solo.
no honestly the point you tell is wrong in too many way. you play with your friend, yes, you are not yet to them point, but honestly it's not that long anymore. it's a lazy way of thinking that is simply i want to get to the end right now! simply no! it's a big mistake to do this.
i'm kinda sure the boost of exp even for the 50-60 will be increase for other jobs then even level up other jobs will not be that long.
if people want to reach the end they have to do the journey... we don't allows people to reach the secret dungeon of FF15 by making them skip the whole story, that the same point here. you purchase a game for all. not only the end game. if they can't enjoy the journey is sad.
skipping the MSQ will make most of the dungeon and raid have no sense for the player, it will have far less impact on you since it will have no background to understand.
an example the death of a npc will have 0 impact if people don't meet them and interact with them throught the msq. i feel people need to grows up and do it.... the msq is not that long, if they want to speed the process they can use the Deep dungeon for reach max level before do it. after this everything will be done in a breath.
before someone say i don't know what i'm talking about, i'm a player of the V1 i had a class 50 when the 2.0 did come out, means i was already ready for go to the end game, but i had to do the whole msq, do i was bothered? no because it did allows me to understand more the world, indeed a few quest of the msq are.... push over, like the part for titan when you must get the food there and there. but with the patch they have work on making the quest better and better. skip this part will alienated the game in the worst way possible! ff14 is a game that grows as you experience the msq, if you make people skip it, it will not be differente than any free to play mmorpg out.