I think challenge from quest could come from most intresting fights and tatics rather than putting tons of monster in a zone and making them super tough , that was bad enough in ff11 i think, hope to not see it in mission based quests in 14.

If you made more party based missions, the request i would make is that you can have npc party members join you if you can't find reallife people and that way you can make a tough boss battle but have support without hours of searching for someone , some people think this idea is agaisnt mmorpg but i am putting it out there because of frustrations i had in ff11.

Guild wars 1 did this and it was never a problem .