I own and compete with several of the guns on your list. Never had any concern whatsoever with the elevation difference you're noticing. Some of mine have been modified to sit lower in the hand than they came from the factory, too. The trigger finger going pointing slightly downward is an unnoticeable non-issue. (For me, of course.)
If you can barely hit paper with an xD or xDM at 15 yds. then that is not a problem with the design of the gun. If your technique is good and your grip, trigger control, and sight picture are adequate, you should be able to keep on the paper at 15 yards with any handgun made. I stand firmly by my recommendation that some good coaching is in order. Most of the time shooters buy new guns, accessories, and have modifications done to solve problems they think are holding them back -- when what they really need is good coaching and a few thousand rounds of ammo.
Having said that, not every gun just suits every shooter. Maybe the xD just isn't for you and something else will give you the feel and the confidence you need to improve.
I will advise that -- after many 10s of 1000s of rounds of practice and competition, and after various controlled tests of my own performance with the guns -- my xDM's trigger (unmodified factory) is much easier to achieve speed and accuracy with than my CZ-75's trigger (slightly modified).
So, if you're looking to buy a different gun to fix your accuracy problems, make sure you do a lot of testing first so you know exactly what you want and what you think it will do for you.