My last front tyre picked up a puncture and when I changes it I was surprised to see that on the inner 2" of the tyre there was absolutely no tread - it was smooth. Decided to look at the other front and it was the same. I had not rotated the tyres at all but I assume from this that I should. I have also read some threads discussing tyre rotation and it seems a must on Subarus. I had about 20,000 miles on the tyres.

yes camber is slightly negative ( I prefere) it gives you a better overall drivebelity

Seems fairly common on the legacys. I know of 3 that do the same wear pattern. If you swap the tires from the inside of the rims to the outside, you can get more life out of them.