Defender is extremely effective in PvP. My highest K/D matches are with this class. Weapons of Light + High Impact Sniper Rifle + Glass House = Golden Gun for 1 whole minute. Not to mention suppressor grenades are one of the best grenades in the game- shut down supers. As for the Striker, it's all about the Lightning Grenades & Armamentarium. If you want to sport a shotgun melee setup, go with Hard Luck Charm (Shot Package + Rifled Barrel + Battle Runner). Get a shotgun kill and speed charge into the next guy. If I were to suggest a buff, it would be to change shockwave into a radial wave instead of a frontwards wave.