Hmm I was on the PTR for about 30 minutes just to test some things out, but I had no luck trying to blink into the mountains like in live. I will try the method you were using on the beta, maybe it is just nerfed and I didn't try hard enough. I'll report back in a few.
About the DMT, I would place one in front of a wall, log out and wait for about 30 seconds, log back in, I would be off the tiger at that point. Next I would wait for the tiger to disappear, place another one, jump on it, log out and did the same again. Only problem was that I couldn't "push" into the wall like in the video. I know with a new expansion there are tons of programming, but it is possible that it somehow got fixed without them knowing. But with new expansions come more tricks and glitches, so maybe they broke something in place of it
EDIT: Ok, so the blinking though walls as a mage has not been fixed on the PTR. I did what Trokair suggested and was able to blink though a wall in Orgrimmar. I think it was because I blinked near the objects and it sent me though the wall.
As for the DMT, I still can't get it to work on the PTR.