I am sorta nervous about how it will work out. A lot of the game's potential depends on the community and it's acceptance of different ideas.
As it is now, at least in FFXI (I can't speak for other MMOs, as I haven't played any others), people only want the most efficient. The job/subjob system allows for a ton of different ideas. There are 20 jobs to choose from, and you can main/sub any combo you desire. Some just work way, way better than others. While a few may offer you some unique playstyles or advantages, the community will -only- accept the combinations that have proven to be the most effective. Try for anything outside of that, and you're screwed, basically.
I think that you are correct in most of what you say here. But there is a reason. A lot of people who are playing FFXI are trying to get the most out of the playtime that they have. (I'm sure this is the same for most MMOs but I couldn't tell you for certain) So they will only use "the best" set-up for the desired outcome. I understood this when I played FFXI, so while seeking a party with my DRG I would be ready with the "desired" sub-jobs. Even if it wasn't exactly how I wanted to use my character. No, I'm not going to get into the fight of "DNC can't ever be a sub for DRG" But to avoid that fight and less party invites I left trying
DRG/DNC to my own time. In solo or campaign. Or in a party of people I've known long enough to say " Hey guys, I wanna try this combo out to see if it's any good. You mind?"
Back to the original point. I think the community is going to be pretty similar, so if you plan on playing from the start then you'll be trying everything out right along with everyone else. If you plan on jumping in after "the norm" has been established (if there is a norm) then you'll have to solo to try out your own special combos or find a group who's not going to care.
Speaking as someone who tried to party as a THF/WHM when I first got my subjob... I'll never judge, so you and your freaky combos are welcome in my party. Unless you keep getting me killed, then you take your weird, good for nothin, watered down, should be using _____ skills instead self and conform or find another party. ;)
The more I train, the harder I get. The harder I get, the more lethal I am. The more lethal I am, the fewer opponents. The fewer opponents, the less to lose. The less to lose, the more I let up. The more I let up, the more room for mistakes. The more room for mistakes, the more I train.