Hey Kyle,
Sounds like a tough one. I am thinking that you are actually having servo issues, even though you have tried different ones in the elevator position. I have seen, and read sooo many problems with the stock servos, it's ridiculous. On my own personal Blade 400, I had an elevator servo lose it's centering right off the bat, on the third battery pack.
When you are substituting the servos, are you using the stock Eflite ones? Do you have any other servos you can try?
The stock DS75 servos have issues with the internal sensor that controls it's centering, and it can make them do very strange things....check out this guys issues with the stock servos;
http://www.youtube.com/watch?v=AhEqWKnCXpU
It certainly sounds like you have covered all the bases, and it may well turn out to be something else besides the servos themselves, but based on my experience so far, the Eflite servos are nothing but trouble! I have long ago replaced all my cyclic servos with JR DS285's, and have not given the servos a second thought since...
Hope this helps, just my 2 cents...
Glenn