My camera settings were f2.8 1/250 and ISO 160 and flash. I thought it was just me thinking that branch did look sharper than his face.
A few thoughts:
1) Af works by generally finding areas of change in contrast and then locking onto them; furthermore when you've got more than one Af point active the camera will always pick the closest thing to it to focus upon. So if in this case you had all AF points active then the main subject in the middle might not be the closest thing it chooses to focus on.
If you only had the middle AF point active though, then it should have had the camera trying to focus on the face area
2) Think of focus like a sheet of paper parallel to the front of the lens. The distance is the point of focus; then the depth of field is the thickness of the paper. So a very wide aperture (small f number) will give you a very thin depth of field (thin paper) whilst a small aperture (big f number) will give you a deeper depth of field (ergo thicker paper - thus more in focus).
Now the depth of field is also influenced by several other factors including distance. The closer you are to a subject the thinner your depth of field is. In macro f 2.8 can be very tiny; making even a slight miss focus way out. In more regular distances at, say f5.6 you get a lot more leeway to work with.
3) Now if you keep point 2 in mind consider also that when your focusing on a very close subject (ergo doing macro and close up photography) you've got 2 kinds of shake taking place. The first is the general up/down left/right motions of your body as you hold the camera and lens (which is always present when hand holding). However the second kind is back/forward motion as well. Because the depths of field are so thin this back/forward motion actually has a noticeable impact.
This general rocking back/forth is a challenge for AF systems to tackle; because in macro its so slight that the AF can find it tricky keeping up. So with f2.8 and even with a single AF point active and your AF in continuous mode (ergo keeps focusing all the time the shutter is half depressed) you can still get a miss focus, which leads us to point 4
4) A lot of close up/macro is done with manual focusing. You focus the lens manually to get the focus on the subject then you gently rock your body back and forth to finalise it. This also lets you have the shutter half depressed the whole time without the AF engaging and causing issues. This is important because when you go the press the shutter to take the shot your hand causes motion to the camera, so the more you are gently squeezing rather than pressing , the less motion is generated.
It takes practice to get used to the back/forth motion as you focus and learning when the press the shutter to get the shot. Sometimes a short burst of shots helps you get the shot you want.
Macro can be a challenge, but is also a lot of fun.
If you're getting a tripod then one thing that will help a lot is a focusing rail. This mounts between the tripod and the camera which lets you move the camera back and forward to help you focus. This is a lot easier than trying to move the tripod legs a little bit back/forward on the ground. Some focusing rail kits come with two sliders so that you can go side to side as well, again helping make it easier in many situations.
An affordable set of rails would be the
Adorama focusing rails, also sold under a slew of other names (basically a single design farmed out to different logos). Searching
Ebay for "macro focusing rails" would give you a whole hose of similar options (and most of the 4 way choices are good).