I thought I was going crazy, but I paid really close attention to my combat log on a Botanica run last night. When this happened, I stopped my combat log immediately (by scrolling up a line) so I could review it after the battle. I had cast a Greater Heal rank 3 on Holyjalapeno, and was charged the casting time and mana, but HJ never received the heal. Combat log was absent any mention of the heal whatsoever.
I don't know how long I've been experiencing this particular little bug, but judging by some posts in the forums, it looks like early March is when this started happening. I started thinking something was up immediately after the 2.1 patch a couple of weeks ago...Here's the main thread:
http://forums.worldofwarcraft.com/inter ... 0141&sid=1
Unfortunately, the only people on the planet to have never experienced this is Blizzard QA, so no fix is in sight.