Likely normal.
But if you live on a 12% grade you really should be gearing down.
I've seen rotors warped in less than two years time on some 4Runners.
You want to see brake dust, buy a BMW. ;-)
Just look at BMW's as you drive. You will see one of two things:
1) Owners who really care for their cars and the front rims look good
or
2) Wheels that have the brake dust burned into the clear coat and look like crap
Prior M3 owner opinion. Great car, horrendous brake dust.
I'll argue Audis are worse, my wife's wheels will never be the same...
I've never noticed much dust from my 4Runner, even early on...