So yesterday I got my first heirloom trinket. It was on mythic UBRS. But for my surprise, what droped was http://www.wowhead.com/item=133597/i...tracking-charm instead of http://www.wowhead.com/item=133598/p...the-third-moon
I was under the impression the very first you get, is always based on your spec. No, I didn't had my loot spec on Havoc. I double checked it.
So,
1) Tank trinket is considered http://www.wowhead.com/item=133597/i...tracking-charm
or
2) The drop is bugged.