I would note that alluvion skirmish (at least from the couple Rala runs of it I remember doing) is... not actually that simple. Unless you've got a bunch of already-geared-up friends to essentially carry you through the event, you are not likely to have a very easy time of it as a "new or returning player"
I haven't ever done Yorcia though so IDK what that's like.
Edited, May 8th 2015 5:33pm by Fynlar
Rala is actually the worst of them, both due to the layout of the maps and some (or ****, all) of the NMs. Cirdas has a similar system, same stone drops, but I would say much easier NMs.
Yorcia is very different. You have a base to defend, and an enemy base to attack. The enemy base will spawn monsters, and by killing local mobs (not the enemy base mobs) you get points to spawn your own monsters from your own base, who will fight enemy monsters and attack their base. One person in the party needs to stay near your base to control the monster spawns, and this is a job that anyone can do, with a little experience or reading up on the event. The other mobs consist of elementals (blm, sch, blu, geo fodder) and small and large butterflies (melee fodder). The whole event is almost a tiny real time strategy game, and much easier to enter into and get the hang of. The biggest rule being to never attack the mobs spawned by the enemy base.
"We are Dragoons, and to make short work of foppish cavalry is our bread and butter."
-Bob Shaftoe, The System of the World