This is indeed the undead hound NM for the BST AF legs, which pops when a BST with the quest flagged and whistle made touches a tomb in Eldeime at D4 (need to enter from the Glacier side). We went after it on Saturday night. Party was BST61 BST61 BST58(me) BLM74 (he's also a BST 60+) RDM/NIN75. We cleared the ghosts in the room first, then popped the NM (Sturm) and his two tiger friends, Taifun and Trombe. The BST60+ charmed the tigers, and we went to work. Battle against Sturm took around 5 minutes, and he's mean as hell, but with the RDM/NIN around we had enough for him.
Only one fight needed, then all the BST with the quest flagged touched the tomb again, and that was that done. You get the BST AF legs right there, no more running around required.
Nice cutscene afterwards - I won't spoil it for folks by giving away what's in it, but it's pretty cool.
Good luck to all that are on this quest, make sure you take a strong party to this fight.