I had a 1600b, and I assume performance should be identical. I'll say first that RF's are very strongly effected by differing conditions...bright sun, haze, dust, angles, reflectivity etc. Also, being very still is super important. So keep that in mind.
But my 1600 could easily do well foliaged trees at 1300 in any reasonable conditions (not fog for example). I hit cows out to 1200 IIRC, but it was hard. 1k, however, not hard if I could be still enough. Max distance I ever got out of it was 1790ish on a tree. But that was pretty rare. Hitting at 15-1600, however, was not.
So while I cannot judge your conditions, I would say that it appears your experience is definitely below what these units are generally capable of. Leica is pretty good about hitting their quoted numbers. I would say a call to Leica would be worth your time.