MMO's are very much about tactics: you need to find the right moment to take a leak.
About needing other players or just party members during some parts of the game: That's not clear to me as well, though I would guess they mean online players. Playing solo may work in the beginning of the game, but as difficulty progresses, I think having party members with you will be vital if you want to survive. But perhaps, if you are the only player in your party, there won't be a timer that will force you to make a choice.
About not having the ability to save: MMO's have always been like that, everything about your character is stored directly to the servers. Dying in MMO's doesn't mean permanently dying. You can never really die, you are either revived or you return to a town or something similar. You won't see a "Game Over" screen. It can be frustrating, however, when you're doing a quest that takes an hour or so, you die without having the ability to revive, meaning you'll have to redo it.
About people leaving your party: if you join people you don't know for a quest, it can certainly be annoying when someone leaves without notifying everyone. Most of the time, if a player leaves, you will be able to continue what you are doing, but obviously, it'll be much harder from there on.
About killing the main boss: the story in an MMO is never finished, and it certainly won't restart. Everyone has his personal story, and everyone plays the overall story at his own pace. If you kill the main boss, only you and your party will be aware of that, but for another party, the main boss will still be there. You may get an honorable mention over the whole server for killing the boss, however.
About names: BioWare has stated they will put a filter on the names; which means no "Darth"'s, no "Revan"'s and other famous Star Wars names. There will always be people who use stupid names, though, for an MMO, that's inevitable.