I used to love grouping up in XI for a party, even if it was sitting in the same camp for a couple of hours. Even the waiting for an invite was worth it, assuming you got into a group that worked well (like a well-oiled machine as it was described earlier). When the party had a great group dynamic that ensured constant killing without too many issues (any hiccups ended up being quite exciting sometimes), it was a fun few hours. The only issue I had, outside of the high probability that you ended up in a terrible party, was that the exp requirements got stupidly high, that even in a strong party it still took a couple of hours per level. With only mob grinding as the way to level up, this got dull and I only ever spent 2-3 hours at the most. I maybe got a level.

With ARR, from what I've seen, I'm expecting that, sure, leveling up is still leveling up and it's going to be a grind. But I anticipate that, and I can deal with that. With the variety of potential exp gaining events and choices, you aren't going to get bored as easily. Get bored of doing some solo quests, get a small group of friends/randoms and do some leves. Bored of those? Do some dungeon runs for a while. You could easily set aside 3 hours on a Saturday/Sunday (assuming you have that time free) and do 1 hour in dungeons, 1 hour on leves/quests, and then finish off with something else like exploring and looking for FATEs.

The only thing I ask is that you don't need to spend hours to get single levels. The exp rewards should be proportional to how much you need and the content you are doing to get said exp. For quests, this should be based on the difficulty of the quest. Gathering some items in a town should give far less than having to go to a remote dungeon to kill a high level NM/boss.