Honestly, most of the stuff from XIV 1.0 was pretty quick to do but challenging at the same time. Ifrit, the story fights, Garuda, etc. If they keep stuff like that up, they'll be fine. It required teamwork, and some coordination, but OVERALL, you only needed 30mins-1 hour to get a few fights done. It was a good balance for non-solo content.
FFXI even had Nyzul which to me was good if you coordinated well with a few people. Log on at X time, hammer out 3-4 floors and that was it, see you again in 4 days! I have no doubt SE can once again manage to have a bit for both groups. I'm in the same boat as Thayos, have far less and appreciate casual content, but also understand the long, time wasting stuff needs to stay for that 16 year old in me who has that drive to play for 8 hours straight every day for the week.
I completed most of what XIV 1.0 had to offer, and felt like it was a challenge for some, but never felt like I wasted 3 hours + doing nothing (Old dynamis, I'm looking your way!). Stuff like the United We Stand fight was beyond fun and could easily be done within an hour once you had your part together. If they want to add Dynamis type events of old, I'm 100% for it. I won't have the time to do it, but, someone else will and possibly get enjoyment out of it. It was kind of neat thing in XI, seeing someone with a relic completed. You'd think to yourself, "Man they have a lot of time on their hands!" and just wish you could have it. I wasn't pissed or anything, actually found it kind of cool.
When you end up in a MMO where all the content is too easy, short and EVERYONE is running around in the same thing, it kind of makes it less exciting. FFXI had that appeal for awhile, where a certain piece of gear meant "Wow, he wasted tons of time to get that!". Sure, some got angry about it, mostly out of jealousy I think and it really created personalities to hate, like, etc, made the world feel alive. Everyone has stories from their server about X guy being a douche, or a great ls leader, etc and you lose some of that when a game goes 100% casual and everyone owns the same stuff. Everyone says FFXI has gone the easy route and there's no challenge left, yet to me there's still items in that game I have 0 chance at getting simply cause I don't have time. These people claim it would be easy to get, yet they don't own the items themselves. The challenge is still there, but just don't look for it.
Anyways, that's my rant for 5:30am.