“Mountain”? Come on, it’s not that much HP, and it’s hardly “free”.
It is a mountain exactly at level 2...why?
Because it is impossible to divide by 3 and round down to the next existing CR... namely 1/2... after that sanity is more or less restored. That was my first fix...
At level 3 the brown bear is much less of an issue.
The other fix I think I would suggest if there is a problem with too many hp would be having the druid receive half the damage the Wildshaped beast took if they leave the form instead of getting all the damage that carried over beyond 0 hp.
Last fix for the ranger if needed: you need to spend your Hit dice to heal the primal beast.
But then you probably need to remove the ability to heal the artificer buddy with mending.