Personally, i think that as long as the pet is at least your lvl or higher, it should do just fine...but there are a LOT of musketeers in marleybone in the beginning, and more meelee enemies later...
I'm guess Bullrogs and Mini-Minotaurs are meant for Buccaneers or Privateers?
It doesn't necessarily matter what pet it is but the talents and powers of the very pet. Such as you could breed up a pet to have attacks, protection, buffs, heals etc. Simply depends how you breed up your pet, and what it'll learn and grant .. Do keep in tact how long to process of breeding a pet can be. I'd suggest going to the morphing tent, once you have an adult pet, and ask a few people to help you out. Best of luck.