Foxes and Dogs are useless pets, both of them are Ferocity pets but their special abilities are screaming PvP ability. So they mixed and match between PvE pets with PvP abilities which is doesn’t work. Getting Dog or Fox in PvE means significant less dps if you compared it to any decent other pure dps PvE pet like cats or wolves. Also using both these pets in PvP is mediocre useless, PvP is about utility and CC in your arsenal you should bring, brining ferocity over cunning pet is wrong you aren’t in dps race there.
There are many pure PvE and PvP pets doing better in both aspects. The mix and match that Blizz doing proves how they don’t know anything about hunters in general other than pleasing hunters who came from Pokémon background, Happy hunting them.
I think you missed the news - though its been repeated oft enough on these boards - all ferocity pets will do the same damage - barring exotics with 2 family abilities, no family ability is damage dealing, so its only a matter of what buffs are covered and which aren't. In 25 man you can pretty much go with whichever pet strikes your fancy.
Mooska (Holy Cow Meatshield) <Lethal> - Argent Dawn EU
Nooska (Blood Elf Animal lover) <Lethal> - Argent Dawn EU
Beast Master hunter in 4.3 - Elitist Jerks
Beast Master hunter, PVE guide - Wowhead