I have an '08 Honda Fit that came with Dunlop SP 31 A/S (crap!) tires. Currently they have 27,800 kms on them and I noticed that all four of them are wearing heavily on the outside. Bad enough so that the outside tread will probably be gone in a couple of thousand kms.
It's not the tire pressure as I check it regularly. The car does not pull to either side or wander.
These tires are not directional, but are marked "outside" as they do have an offset tread pattern. At least I believe that is how you would describe them.

So what's up with this tread wear? They are crappy tires: very noisy, worse than the snow tires, and have terrible traction on wet roads.

 

doing a lot of canyon carving?

get an alignment and post up the AFTER values.

 

I have crappy Dunlop's too, worst I've ever owned. I know you said your car doesnt' pull to one side but maybe get an alignment anyway. Either that or your camber is off.

 

My mother's Dodge Magnum had exactly the same problem, but only on the front wheels. It took a trip to Dodge to tell us we were within spec, and a trip to Goodyear to get the wheels properly aligned. Not saying only goodyear does a good job, but make sure you pick someone good. It also might help to have the alignment specs handy when you talk to a tire place. I used to have that thread bookmarked for alignment, lost it.

 

Since the tires are almost worn out, suggest letting things remain status quo until they need to be replaced. Then have an 4-wheel realignment done when new tires are installed.

 

If everything on your car is stock even the tire pressure... then you have toe out...