Ideally, I want grouping for xp and big missions (think main storyline missions compared to random quests in FFXI), and soloing for most other things aside from maybe NMs and other things of that nature.
I play mainly support and tanking jobs, which are not generally solo-friendly. When I get the retail version of FFXIV I can almost guarantee that I'll play a healer first, then a tanking job, then a support job of some sort if one is available by then. I just can't imagine how I'm going to solo well as a WHM.
In FFXI I have a 75 WHM, RDM, COR, BRD, PLD and SMN (with a 68 SAM) and I rarely have issues finding a party. I understand that I played high demand jobs, but I also usually built my own party instead of sitting around waiting for invites like a vast majority of people did, and complained about.
My only real issue with FFXI partying is the fact that you really only had one "good" tank for xp parties. NIN can't hold hate well until endgame and WAR isn't a very good tank post-37. That left with you with PLD, unless people were willing to experiment with MNK or SAM, which rarely happened. SE kept adding more DD and support jobs, but never another tanking job. Very displeased with that, and I hope there's more of a balance in XIV.