Maybe that's beacuse defenter is only character in destiny which is team-focused. my teammates enjoy my bubble generating orbs for them, as well as from my malee kills and heavy kills. I'm maybe not that great and friendly person, but definitely you can count on my support and agressivnes in getting enamies away from you and focus on me ;) In pvp striker is easy to prevent, just shoot me from distace or bladedance/novabomb me ;)