Good day folks,
as a melee, solo and at level Stonejaw hurts bad and it takes a while until you beat him down.
Good positioning helps. But you should have around 250 hp on heroic nevertheless.
So there is a group of trees you can take advantage of. I parked a hire there and he was safe from attacks but was close enough to heal. (right red arrow)
I tried running around Stonejaw in circles but he got 1 or 2 good hits anyway. Best strategy for melee imo is to get in his face as close as possible. It will look like you're fighting his scrotum. Don't worry that is the right spot. He will barely be able to make his special stomping or roar attack.
If you need a safe spot to take a breather jump through the 2 trees to the left (yellow arrow). It is a bit tricky to stand correctly but Mr. TRex can't attack you from the other side.
Hope this helps a bit.
Cheers,
Titus