Trion, please don't make players have to have an online pass.
Defiance will be a MMO that will attract gamers of all sorts. That means that they will be playing the multiplayer.
But if I understand right, there will be a season pass for DLC.
If you require an online pass for the game being bought used, then chances are that they will not want to spend any more money and get the DLC. If you have a game that's truly fun, addicting, and really keeps on going, then they will want to buy the DLC when there isn't an online pass in the way, which means more money for you guys. When they get the DLC pass, then they will most likely keep the game and keep playing it, which means used game sales won't happen as much anyway.
Used sales will happen wether you like it or not. If you impose an online pass, then it will slow down used sales and possible profits for the DLC.
Take Call of Duty for example. They have DLC passes and they don't have online passes, but yet they are the highest selling entertainment titles of ALL TIME world wide!