The thing with that prey is that it happens in a period with a ton of other crap happening on the screen at the same time and is very easy to miss if you're not looking for it. Though by now, healers who've been running it constantly should be familiar enough to know and expect that it is coming that they know to shield and use instant heals on the target. I admit during the first weeks of 3.4 I really couldn't reliably save the preyed target but now it's very easy with to heal through it.