It's really not new, unfortunately. Usually it's from targeting the person and then hitting the button within an unnoticable second of each other, or at the same time. I'm prone to it when there's a lot going on and chaos on HP bars - one hand doesn't keep up with the other or both hands aren't keeping up with what my brain is telling them to do..... or lag is keeping it from doing any good.

I've noticed, since Heavensward, that some of my heals just go -no where- (rare, thankfully). The cure didn't even land on myself (as usually happens now and then) and no graphic or gained HP on the person I casted on. It just..... went nowhere. Cast bar, makes the casted animation and then.......... blank. Had this happen in Aery and T5 just before maint (5 and a half-manning, solo healing and solo tanking T5 and then again in a hurried, chain-pulling run in Aery *Twitch* Not good for heals to not go through).
It wasn't out of range or line of sight - the receiver and I were stationary - as well as able to receive a follow-up cure. Probably lag. My 'blank' cast incidents may also be a graphical glitch - I noticed that some NPCs 'disappear' when you take off but were there when you were on land. I also noticed some of my Holys not hitting, even though I'm practically on top of the mob I'm trying to stun. >_> No damage given, no animation reaction to being hit and no stun. I might as well have been 100 yalms away when I holy'd.