They made it harder. Multiple people confirmed, (including me). It must be one of those stealthy changes. I was switching mounts like crazy on different toons to beat it. Maybe the mounts are spawning faster now. I don't know. I have to switch mounts when one of my toons' mount is around 15-20% HP. Otherwise, he will get unhorsed and 2 shots. And I switched 2-3 times on each toon.