Tokina 11-16mm initial issues???
The Tokina is built like a tank and is wonderfully sharp wide open but yes, it can be a little tricky when it comes to AF. One trick I picked up on the web that seems to help is to focus on your hand before focusing on a distant subject - the theory being that the AF appears to be more accurate when focussing from near to far than from far to near, and this forces the former state. I started doing this and whilst I can't say that it works definitively, I do seem get more keepers this way (then again, I'm now more experienced using the lens / the hand thing slows me down and makes me think more so it could be a placebo effect). The only downsides of this approach are an above average number of accidental 'hand' shots and the occasional strange look from fellow photographers