My 70-300mm lens and I have been having issues. Just when I think it is HIS fault, he goes and shows off by focusing beautifully on a random fly that wanders into the frame (he has done this TWICE!).
This is just a small cropped corner of a larger group of flowers (this was from last weekend- how come we all want to photograph bees, but not flies?). So obviously, we have a SITUATION, and, since I focus MANUALLY in macro, there just might possibly be some user error going on here . . .
So today I tried again. I hooked my gorillapod around a chair and then sat in the chair and lightly held on to the gorillapod (because I am always afraid the camera will tip over because of the long lens). I had to scoot the chair back and forth to find the perfect focus and managed to do BETTER this time.
There is such a narrow depth of field in macro. The back of the yellow flower center is in focus, not the front. I had to use a high ISO, because I was inside on a rainy day. I think I can do better in the sunshine. But I am encouraged- and no longer mad at my lens.
f/5.6, 1/80, ISO 2500 at 300mm
melinda anderson photography 
This is fabulous! The focus and depth of field are excellent. I’m glad you don’t have issues with your long lens any more. And how ironic that your first photo is almost the same thing I posted today!