In the wow gold game, this appears to be a glitch.
Time it so that his health ticks to 7,000 at the exact moment the Tame Beast finishes channeling.They must overlap at the exact second for the Worgen buff to stick. If done correctly, he will actually transform into a Worgen just after the taming is complete.Timing varies by the Hunter's level and damage output. This will take a number of tries to figure out. The popular strategy for level 80's is to work down his health until about 56%, then use Wyvern Sting. This will put him to sleep for 30 seconds. Watch the time remaining on the sting. When there is about 14 seconds left, start using Tame Beast. When he wakes up, in the last couple seconds of taming, Wyvern Sting has a DoT causing nature damage. If timed correctly, it will give a tick of damage to bring him to the right level when Tame Beast finishes. It may also be possible to use Serpent Sting.It has been reported that entering an arena with this pet will reset him to wolf form. If you are lucky enough to tame him in Worgen form, do not take him into arenas. So far, the form does not seem to be broken by leveling him, when he dies, stabling him or loading other zones besides arenas.In the wow gold game, this appears to be a glitch. There is speculation and fear that Blizzard will fix this glitch, meaning that all of the Garwals out there will be reset to wolf form.