Without trying to recover all thats been said the 1st thing to realize is that the merge starts once you hit icon range. If you need to make a sudden move at D800 then you messed up long before that. The general rules that govern a "dog fight" apply on the merge. You are in some combination of "in plane", "out of plane", "lag", "lead" or "pure" pursuit. A good pilot is looking for some type of vertical and horizontal offset. He doesn't want to be flying right at the bogey but in the opponents general direction with the nose pointed a to one side and higher or lower.
This creates a measure of separation in the relative flight paths, in a merge with 2 good sticks then normally you'll see both pilots flying some type of pursuit curve to the merge point. Based on circumstance, plane type and preferred fight each pilot will react to the other pilots change in posture (the variables above) in order to either maximize his advantage or minimize his disadvantage (this is critical, good pilots often win fights that they start at a disadvantage in).
Here is a link to film clip that I use to try and help newer sticks get a better idea. I'm in an "inferior" plane in a -E position vs a 4 x 20mm bird. I can't afford a "joust" and I'd killed the other guy just before and he was squawking on 200.
So my perception is that either he was gonna come in looking to light me up or he'd try and stand off and go "face to face" until he scored with his 20mm's. I used my greatest asset (the perception of weakness my "inferior" ride offered) to lure him into a poor shot window.
This is a timing issue that's not really easy to learn in the TA now since the damage is off but back when I was a trainer the TA had normal damage. It is very possible to absorb some lead and take no damage (which may or may not be historically correct). The key element is in understanding and applying two concepts "out of plane manuevering" and "variable G loading". If you present a shot window under conditions that combine both flight paths being out of sync (crossing paths vs one following the other) with a changing G load that forces the bogey to shoot while changing the amount of G's he has to pull to maintain lead it becomes very difficult to score any effective hits. If you combine that with a flight path that encourages an overshoot you now put yourself in a position where if the bogey takes "your shot" he has minimized any chance for success while creating his own problem.
I'm far from the best at this but this clip gives you an idea of what a -E "Hotel California" merge looks like {they come in but they never leave}. The Nikki takes the bait "misses" the shot and ends up with a P-40B hemorrhoid that won't just go away...
http://www.az-dsl.com/snaphook/P40vN1ki.ahf
