You know the saying about the best offense. That describes you perhaps best of all. You excel at assisting allies, but you also hinder foes. While you are able to attack at quite a range, you're not built for close combat. The best offense is indeed a good defense, but in your case, you may need to rely on your teammates when it comes to the former.
You are one of the most team-dependent Archetypes. Along with the Tanker, you really shine when you can help your allies win fights and bounce back from injuries. However, you also become more potent yourself as your teammates struggle. Whenever you begin your turn and at least one creature that you can see within 50 feet that is not hostile toward you is below one half of its maximum hit points, you can restore a number of your own Endurance Dice equal to one half of your Proficiency Bonus (round down). You can only do this once per round on your turn, regardless of how many injured allies are present, and you cannot exceed your maximum Endurance Dice with it.
In addition, if no more than one non-hostile creature that you can see is within 20 feet of you, you gain a bonus to the damage you deal. Any Primary or Secondary Power Set feature that deals damage gains a bonus to the damage roll equal to your Proficiency Modifier. You select the one friendly creatures to exclude from this effect, even if it is within 30 feet. This increases to two friendly creatures at 9th level and three friendly creatures at 17th level.
As a Defender, you gain the following features.
Hit Points
Saving Throws: Dexterity, Wisdom
Skills: Choose two from History
Attack Save DC = 8 + your Proficiency Bonus + your Wisdom modifier. This is the DC for any Saving Throws prompted by features from any Power Sets for this Archetype.
Defenders have the following Power Sets.