A few things to add-
Your opponent doesn't need to be faster than you to get a decent overshoot... He just needs to have a decent "rate of closure". He can be equal to you (or even slower for that matter) in speed and still overshoot, if you adjust his angle of approach by changing your heading. In short, turn so he approaches from your side, instead of having him on your six. Even if you're both at 250 mph, he'll be closing on you at a high rate, instead of being saddled up on your six.
Showing him your side profile is a tougher shot, since he needs to lead you (and making him pull lead on you makes the overshoot easier). As he hits about D800 pull up a few (10-15) degrees, and transition into a barrel roll.
You'll want to be keeping your speed up (maintaining E) and at the same time giving him ways to burn his E, with the goal of equalizing E states, and getting behind him with enough E to kill him. So, slowing down to get the overshoot is something I normally find detrimental. I'd rather keep/build my E/speed and get overshoots by angles instead of by "braking".
Also, a good offense is the best defense. Be looking for a way to get the upper hand, rather than to just dodge his shots. Be thinking "how can I use this situation to my advantage". I'll generally use the barrel roll to dodge his shot, but also as a way to get behind him. He'll generally have enough speed to pull away and try again, so at some point I'm going to want to be able to transition into a more "normal" merge if the fight lasts long enough.