Just killed Bonemass and all 3 bosses have been a complete joke.

Eikthyr – Just run around stone walls shooting arrows at the deer because they stop the lightning attack, very easy.

Elder – Same thing as 1st boss, he only has 2 attacks if you use a bow, the black thing he throws at you doesn't go through stone, if he summons roots you simply run to another pillar and keep shooting arrows – very easy.

Bonemass – Since he takes little to no damage from bow/arrow, you have to melee but that's okay because he's still easy. Wait for him to do the poison gas attack, run in and block his first melee, then melee attack him 4-5 times or so and then run out or you can choose to block the 2nd melee and hit him again, then run out and wait for the poison attack to happen again and then run back in, very simple and you just rinse and repeat until he's dead. Skeletons/blobs aren't going to do any damage if you have an upgraded iron mace/shield. The fight was too easy.

I play solo and so far these 3 bosses have been underwhelming. They have 2 or 3 attacks and they're so predictable. I hope the next 2 are more challenging.