I use an Infinite whelping on the Bear - as long as you don't get stunned on the first hit from the bear you'll win. If you get stunned bail on the fight until you don't get stunned.
1. Only use tail sweep - you can heal your Whelp if the bears hp is lower then 330hp when the bear hibernates to heal himself.
2. You want to have low HP to use early advantage on the Major Payne's Tonk, this hits for extra damage against Mechanical. Many times the Whelp will take out the Tonk as well as the bear. If not the Tonk has low HP and you can take him out with your next pet.
I use 2 pets for this fight and a lowby at level 20 or so. Just in case my lowby need to take or even gie a hit.