Defenders are the most underpowered class in PVP IMHO. Unless you are playing against some serious dimwits, your opponents will either just avoid your bubble or take it out with their own super. Strikers, on the other hand, are an excellent PVP class. I played on my brother's a few weeks back and was crushing the other team. Learn to use should charge for more than just OHK'ing your opponents; use it as a way to create and close space between you and your opponent and you will be more successful with it. You can also use it to OHK people who are backed against a wall :)