With the lens in full manual focusing mode, are you able to get far objects sharp by manually focusing and using 5x or 10x live view image zoom? As for autofocus, if it is having trouble with infinity or with accurate focus in general, you should try calibrating your microadjustment for that lens. It is not uncommon for this to be necessary, and I would think it would be especially important for super wide lenses given the low depth of focus tolerance that comes with short focal lengths.

I shot a few stills on my tokina 11-16 a week ago and noticed some of my shots focused shorter than intended, but i havent had a chance to look into it, and I suspect it could just be an issue of me not shooting stills with my 7d very much (I primarily use it for video), but it could be a microadjustment issue otherwise.

Microadjustment? What's that and how do you do it?

Menu -> C.Fn III -> 5 It's used to compensate for small errors in AF of each lens. It more of use for still than video I would think.