I was actually originally "attacked" if you will, for removing the vampiric batling FROM the guide that I rewrote in spite of the fact that nobody can ever get it again. The pet I replaced it with did just as well, in the end, but still some were annoyed (oddly, none of them had picked up the guide and rewritten it themselves). I stuck to my guns and the guide is still quite useful (and in the process of being updated, pending approval for how to post it).
So you're more likely to not see the pets that cost real-world money (or can no longer be acquired) used in most guides because the idea is to make guides usable to the masses, and not for the elite/wealthy/haves. Nothing against those that have them (I have a goodly number of them), it's just no fun finding a great guide only to realize if you never bought the WoW Collector's Edition, attended the 3rd Blizzcon, or won the lottery you can't follow it.
Unfortunately that leaves those people who did get all these kinds of pets to experiment on their own, returning to your question as to how to make them useful. Which is hard because many of those pets have extremely unique moves or move sets, so they don't just cookie-cutter replace any other pet.