The druids can be explained: Their bear form is that of a black bear which has indeed 19 HP in the MM, while the player for some reason gets to transform into a polar bear (42 HP).
I think the druid bear forms are a holdover from the patch before the druids were released.
They are turning into the same bear as the ranger gets for a companion, but the druid bear form ended up being stronger.
Which, to my way of thinking, means the druids in the grove need that adjustment.
