There are several issues to this topic as I see it.
First of all, the quests - as mentioned - are way to easy. The only thing that makes a couple of them difficult, are the location of the quest itself.
So they should redistribute some of the monsters to better suit the paths to different leves. I am not saying that the road should be free of monsters, but it should be monsters that you are able to kill yourself at r46 with difficulty, but rather easy/easier with a party of 3 f. ex - like one tank, one DD and one healer.
That way you would also make it more logical to team up for quests.
I still remember the time spent doing the r46 main mission due to the fact that you had to sneak by several mobs that were way too high rank to be able to kill them with some difficulty. It seems like it is either too hard or too easy, but nothing inbetween.
I found that they solved this rather neatly for the local leves though, as they moved the delivery-location of several leves to better adjust to the rank of the leve.
Heck, there are even times where you are unable to complete leves in Nophica's Well due to the placement of a NM.
Another issue - if they state that it is easy due to casual players - or even for the DoL/DoH: Running for 1 1/2 hour to reach a location, as well as spending time waiting for mobs to move out of your path, you ensure that a casual player perhaps only will be doing that quest and one set of leves through one week, as they do not have time for more.
If the monsters had been adjusted, a DoL/DoH could dodge the attacks from the mobs by running in somewhat clever way, and adding the option to teleport to a specific location that is closer to the final destination, would lower the time it takes to complete the quests, which would make it a bit easier for the casual players.
A more hardcore player would be killing the mobs on the way for the challenge I would believe.
Also: adjustments to the quest based on your class would ensure that it is a bit more mobs/figthing for a DoW/DoM rather than for DoH/DoL.
There is one quests were you can choose to either fight or parley, this is a clever solution that could be implemeted elsewhere.
What about creating leves and quests that suggest a light party or a full party (based on updates that are to come the 14th of April)? I know some of the NM chain-leves do require a bigger PT, which is great in my opinion. This make players do stuff together for the fun and demand of it, not only to leve-link to get optimized SP.
yay for more challenges - and more quests in general - that will give the players some drive. At the current state, it is more or less easy quests and grinding that is on the menu.
I love the game, and think it has an awesome potential.
Well, my two cents at least.