I haven't played an amazing deathstroke yet, but against most online deathstrokes i did find that if you spam DF1, you will be relatively safe. he can't start up his gunshots until you stop(you cannot trade bullets though you will lose), I think the only thing that could stop you would be low deathstroke gunshot, but can he input it while ducking? Also, harley actually inches herself forward with every shot, so when you have them scared.. you can jumping db1 and hit them with gunshot which is overhead, or even better go for the mixup when they're hesitant. I feel the gun is underestimated. The best thing is to frustrate deathstroke before he gets you.. Harley can do it! I know this isn't the only thing, cupcake bombs and meaty neutral jump 2 will blow up deathsroke too in the close up game. if you land 112 silly slide you can neutral jump and meaty your jump in because i'm pretty sure they can't tech roll 112. Hope this helps!