That is actually very bad target priority Ugh. You make it to level 4's and start popping the BS's first and you'll find yourself floating home in pods because the bigger ships are usually the ones that make the next waves spawn when they are popped. Secondly, the frigates are priority number one in missions because they will web you which means all the other rats are doing even more damage because you are going so slow. They will also point you so that you cant warp out (depending on the rats), so ALWAYS ALWAYS ALWAYS kill the frigates first. How you do so is completely up to you though.