I'd just like to bring up the Duty Finder that will be available at launch, since no one seems to be discussing that yet. If your concern is that there won't be enough people on the server at your level to get through low level content, you don't have to rely on the promises of the higher level community. The Duty Finder will let you party with anyone who's looking for a party no matter what server they're on, and from what I understand the Duty Finder will cover any and all instanced content that can be done in a party.
So there should be no reason to worry that you won't be able to find a group for a dungeon. Pretty much everything else is soloable except for maybe FATEs (which are adjusted to the amount of people in the zone you're in anyway), and you don't have to be a certain level to participate in roleplay.
So unless you're really attached to a certain group of friends who won't be rolling on an RP server, or you really don't feel like starting your character in an established economy, there really is no reason to be apprehensive about joining a legacy server.
So there should be no reason to worry that you won't be able to find a group for a dungeon. Pretty much everything else is soloable except for maybe FATEs (which are adjusted to the amount of people in the zone you're in anyway), and you don't have to be a certain level to participate in roleplay.
So unless you're really attached to a certain group of friends who won't be rolling on an RP server, or you really don't feel like starting your character in an established economy, there really is no reason to be apprehensive about joining a legacy server.