Once again I wanted to chim in on this issue. I am a 70d owner with the same issues, and some other annoying issues with some simple stuff that canon left out, like a frame counter. But I will focus on the issue at hand. Yes, there are issues with this system dispite what canon and some owners may say but since we are stuck with them we can make the best of it.
I know that multiple focal points are one of canons selling features but I have found that they only serve to confuse the system. Use one focal point. You can move it anywhere in the frame you want but only use one. Second, it is not a full frame camera so we will naturally loose a stop (about, as a guess). In addition the focus is not as precise as we are led to believe. So my solution is to forget about any apeture larger than f8. F8 seems to give me the same depth as about f5-ish. I get about the right depth for a good portrait but still get a sharp subject. My science my be a little suspect but trail and error results seem to work well.
The 70d is not as versital as I really need and I still use my 5d Mk1 for almost everything, but it can be used. Trying to snap the white board for a custom white balance never works, and it has a few other annoying issues but at least I can work with that one.
