My druid Lilindi has a badger, it's never been killed, and she made it to 16th without needing it as a meatshield. Right now it's following her around Port-a-Lucine, because she hasn't found a safe place she can leave it there yet. She was a complete pacifist when the mists took her, and a combat oriented companion wouldn't have made any sense for her.
Maria has a hell hound. She's evil, she's a summoner, and it fit the backstory of the character. It's been used in PvM once, and to kill and eat some thugs once.
Dribo had a faerie dragon, it was used in PvM twice, and was never so much as injured. Again, it fit the character.
Wilhelm, my first character here, a fighter/wizard, has a panther. It's been used in PvM quite a bit, got killed many times when he was mid level (5th to 12th, really), but then again, he got killed quite often too, being my first character here. It also fit his character, since he was a follower of Bast when he got it.
If the character in question is a loner, take a familiar to reflect that. Rats, wolves, hell hounds, and such, are all pack animals. Yes, it should be survivable if it's going to be used in PvM, but it should also make sense to be bonded to the character.