WoW's greatest asset is that it is not just a race to cap, or race to get lvls, or a farming session. With quests giving, money xp, and equipment, WoW is actually a good RPG, not just a good intereface for gamers to get together and play. That is how i view ffxi now, it was an interface for people who liked to get together with lots of other people and participate. This is a GAME, this is fun. You explore, you do quests that are fun and rewarding. Grouping is more leniant from what i have seen.
Experience from quests is scaled, this means that,(at least so far), the leveling times remain fairly similar, and you dont need to set aside 5+ hours in a row to make significant gains, you can get portions of quests done for future xp, equip, money, you cna do 1 or 2 quests in 20 minutes. This game allows a casual gaming experience, or a long set of time, with each being fun.
In addition there is a rest system to help more casual players keep their lvls coming smoothly, (basically it increases the amount of xp you g et per kill for a certain total xp amount, which isbased on your rest time. As an example, if you rest for a week RL, you will get 200% xp per kill for 1.5 lvls, (straight from manual).
The reason why jobs aren't cookie cutter is because of the talent system, see Diablo2, 3 different speciality trees, see the wow site for more info on that, but the equipment doesnt make the character, the talent choices do. And efficiency isnt a big deal, because lvling on monsters that arent that difficult is highly possible. There is really never, nothing to do in WoW , literally. Unlike ffxi where farming is gooduse, or waiting for groups or people, or traveling, it is all very seemless, and farming is irrelevant except maybe for tradeskills, wich are alot more personal anyway.
8-10 characters per one monthly fee.
Only need 1, more is just fun, this game encourages trying new things, and it is fun to, no redoing chocobo crap, subjob crap, rank 5 crap. So far no real boundries like that. Mules dont seem to be neccessary, cause money isnt hard to come by, and is much less player economy.
New character doesnt just = new job, but rather new character = new adventure, like i said, this is actually jsut a good rpg, and it feels that way. Restarting ff7 to use different people in group for instance.
I will say this, player skill, is not as big of an issue, at least not so far:lvl 20 in open beta. Mistakes arent as lethal, and dying is not very penalizing.