A properly spec'd hunter pet should be tankier than a voidwalker and have higher DPS/TPS. However, warlocks are much stronger picks for boxing IMO.
The only thing that would prevent you from being able to clear dungeons is if the threat value on torment/growl is too low to keep agro on the pet. I know it worked on "unofficial" servers but we won't know whether those threat values were accurate until somebody tests it on classic. Put your first 8 talent points into demonology for improved voidwalker and give it a try.
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