Direhorn in a China Shop

The [npc=69193] is found in the northern part of The Beast Pens, by the pool where the [npc=67576] are. You'll need to kite it to the Delicate Zandalari Vase to the southwest.

[npc=69193] moves very slowly. It is also accompanied by a [npc=69302], which when killed, will turn the [npc=69193] into a friendly dinosaur...so don't do that.

He casts [spell=138768] very frequently on the PTR--but you are looking specifically for his [spell=138769] attack to smash the vase. He won't cast the Charge if you are within 15 yards of him.

Okay, this one took me a while. Some extra info I hope you find useful:

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• It's doable since the phase 1 of the Isle of Thunder.
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• Vase coords are 49, 39 (sorry, my addon doesn't give me decimals).
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• Keep hitting the bloodhorn, he will evade and go back if you don't (though he will enter in combat again without getting back the original position if you are near him).
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• You have to use his CHARGE ability, not the puncture one (as Perculia said). This one is important.
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• The vase doesn't sparkle and it's not enlightened nor the cursor changes when you mouse over it, but it shows a tooltip ("Priceless Zandalari Vase").
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And I think that's all. Happy achievement hunting! ^^

For those still having trouble getting to the spot for this achievement see: Here
Video representation of how this achieve is done (pre-stage 3).
The reason it is so hard for some to do this is because in reality, this achievement is supposed to be unlocked in the latter stages of the isle. HOWEVER it is still possible to do it when your realm is on stage 1 or 2.