I am very happy you liked it! What activities did you choose for Sarah? I wanted to make act3 a bit leaner since there is so much story that needed to get done, I still like grinding so my compromise was to make a dedicated area for people such as me who just like to see numbers go up, thus the grinding hole.
If you do not grind at all and enter at lvl 17 the bosses you mentioned are punishing, if you do grind they naturally become a lot easier but all of the main skills are gotten at the levels you naturally would get as you progress through the story (and use the free level-up items). It can be cleared without them but it is a challenge.
If you have any particular opinions on the narrative I would love to hear them.