The best advice I can give you regarding the Minfernal is to find a non-CRZ realm and roll a DK. That way there will be far less competition for the pet.
I got so desperate for this pet that I went this route in the end. Found a low-pop, non-CRZ, Spanish speaking RPPVP realm (which is going to be pretty quiet right??) and rolled a DK. It only took me an hour or so to level out of the starting area and get the DK to Felwood. I got super lucky as there was a Minfernal waiting when I arrived but it generally should be much easier than regular realms.