Posted here as I was unsure where else. After patching, there were a few woes, but disabling/enabling addons seemed to clear these. I did download Boss Panel, but that's the only addon. I now sometimes get this:
I noticed that also last night. I also found how to duplicate it. After you kill a mob and loot it mouse over it again and that is the tool tip you get. This only happens the first time you mouse over a dead body, at least for me.