Get rid of nextInt?
Other than that some things to make kill aura better:
1. Use longs and system time for more dependable kill aura speed.
2. Rather than EntityPlayer have it "if(isTargetable(e))" then make a boolean with the constructor entityLiving e and make it return true if it's a player, mob, or friendly creature based on booleans determining if you should attack the entity type.
3. Use packet 12 instead of 13 as it will cause problems on NC+. Then just use yaw and pitch for the parameters.
4. Have range and the delay speed changeable (chat commands?)