My two cents:

I believe the main scenario quests have been specifically designed so that you can get through them either by fighting or finding another way, thus actually allowing people who have land or hand as their main job to partake in the mission. An example is the mission (trying to avoid spoilers here) where you can either fight the baddies or parley off with their leaders in the cave to avoid "all firey hell breaking loose".
It is the guild-based missions that can flesh out combat, gathering or crafting requirements.

I am of the opinion that the guild quests need to do more of this fleshing-out with more quests being played out through the guilds to greater contribute to the whole of the story and lore of Eorzea, which you can then only get in full detail if you explore all the guilds.

I also believe that main scenario quests should trigger at physical levels rather than one's lead class rank. If no prowess with any particular class is required for the main scenario, people shouldn't be held back from the main scenario quests that form the backbone of the story for diversifying into other classes.