You are right Hoople, I got 15k on a rear once, but there wasn't many spots on it with tread. Too, too dangerous. Slipped around alot. I'll never do that again. I'm averaging 8k to 11k on the last three. Still using thr stock Dunlops.My guess,,,,, at 16,000 miles there is no tread for rain in the center area of the tire. That's not for me. I'm at the middle of my 3rd rear tire with 20,000 miles on the bike. I got a little more milage out of the factory stock Dunlop tire but I like the softer compound of the ME880's in the rain. I think what your getting for milage is not far from normal.
It also depends where you live. In ElPaso Texas where it rains 3 days a year, I might push it further.