I had a similar issue with tyres when I bought my Yaris in 2006. Car went in for its 1st service at 15000km for me to be told that I only had 2mm left on each of the front tyres. I went ballistic!!They were Dunlop Hydro something - turns out that tyres are made a lot softer these days, better grip apparently....but not longevity! Toyota dealer changed the front 2 FOC for Goodyear - made by Dunlop too -car has just been in for its 30000km service and front 2 are perfect 5mm on each.
A lot of the problem is the state of the roads but I've found Goodyear to be great so far, used Continental in the past and got good mileage out of them. Hope this helps.