That really doesn't explain the general feeling from the rest of the t13 armor of 'if we want anyone to actually see our new work, we need to kick it up a notch!.'

No, it just seems that they never came up with a good, workable idea for the DKs in the timeframe they got. Which honestly doesn't bode well for MoP tiers for them, although I expect that at the very least the first tier in the xpac will have a distinctly east-asian feel to them to shake things up.

The only sets that seem bland to me are the Druid and DK sets. The Druid set is understandable since it's supposed to be all earthy and dirt/leaf/vine themed. Kinda hard to make that really flashy.

Transmog is going to act as a sort of measuring tape for the devs regarding what we, as players, like on our gear. If 75% of Warlocks cover up their T14, for example, by transmitting to something else, it tells the devs that people generally didn't like it. As an artist designing these armor sets, it means they need to step up their game and come up with really awesome ideas if they want people to use it.

Maybe that's where my issue lies; my main is a druid, and I feel like the T13 is boring. Leafy or not, we've had some really good sets in the past (T6 was great, and I actually liked the Sailor Moon helm on T9). I liked T11 for the colors and the shoulders, T12 was fine except I missed my robe (sorry boys, I like the dress). T13 just feels like it falls short of that.

I also saw rogues complaining about theirs, but they've got legendary daggers, so pffft.