Defenders all serve the same role in combat: Base yourself with the enemies and keep them from going after your less armored teammates. That being said, any defender can do any of those things. It's just a matter of how flavorful you want the character to be. Some races are better suited for certain classes. (IE - Dragonborn make better Paladins, Genasi make better Swordmages, and Goliaths, Warforges, and Minators make better Fighters)
That being said, there're plenty of good Paragon paths in the PhB 1. My guess is that you just haven't found anything you find particularly interesting to play. If that's the case, then pick up a copy of the Forgotten Realms Players Guide, Martial Power, and/or PhB 2. All have the stuff you need for Paragon Paths, as well as all the alternate class abilities that can make your PC more interesting to play.