Hmm don't really understand this macro.
In case of wipe in raid the pet will die anyway. if you have the time, desmiss pet then FD.
If you are in panic and wanne run away, better to keep pet fighting to give yourself some distence and FD then let pet die. You can allways bring your pet back if you keep yourself aliwe.
If you FD and your pet comes up to you do to petfollow, and have mobs following, you sometimes get aoe effects from mobs killing your pet and you find yourself not i FD mode anymore and if thats happends you will find yourself running for your corps pretty soon.