FYI, I invested in a proper depth measure at the weekend and checked mine as I'm thinking about changing them. The fronts are at 4mm, the rears at about 4.5 to 5mm, that's after just over 30k miles and they've not been rotated. If anything, these have worn less than the same tyres on my old CX5, which I had to change at 33k as they were down to the indicators (long story involving there being no Toyo tyres in the UK in that size at the time...) By comparison, my previous Forester went back at 75k miles/3yrs with the original tyres on (Geolandars), still well on the legal side.
Alan