A few guys on this thread came from BMS. F-16 is nice and retains energy super well because of the AOA limiter. The F-15 has no such limiter so you can bring the AOA really high when you need to. Personally, I think its an advantage.
I was like you when I first started out. The Eagle bleeds energy fast only because you are pulling back all the way. If you only pull it half way back, you'll retain energy well. My advice to you is to merge above 400 KTS. Also don't be too set on retaining energy. When you need to snap that nose around, don't be afraid to bleed off your energy. It's all about timing. Get on his six, get the shot, and kill him asap. Another important thing to note is that the eagle rolls super fast. I've had Mirages jump me and turned the fight around for guns kills because I know how to turn and burn when I need to. Rolling will throw the guy's aim off. Just about every other 4th gen fighter in DCS will out turn the eagle sustained or instantaneous. Take the SU-27 for example. The only way you are going to beat a flanker in a dogfight is to be a better pilot than him. The Flanker will out turn the eagle at any speed right up to mach .8 or something. Just know when to time a really quick turn, and you can win the fight. Otherwise my only advice to you is kill the target way before the merge. The Eagle is the best BVR platform in DCS.