did i do something wrong?

why does the dk that bailed on us as soon as she got what she wanted from naxx but came back right before ulduar keep getting raid invites over me?

is it cause i'm shadow? is it cause i can only top out at 3.7k dps on some bosses? did i make the chick who does raid invites mad somehow? does she want me to stop rolling on gear that would better help mages and warlocks, who can pump out the really big numbers, so they can pump out even bigger numbers? i NEVER stand in the flame wall, i get away from people when i have the light bomb, and 9 times out of 10 when they call to wipe it, i'm still alive.