My guess is Larian is testing mid-late game mechanics during EA as a means to further goof-proof the system without revealing Act 1 (remaining), 2, and 3 content. I have also killed everything available using only Shadowheart and a PC Ranger, only using 2 or 3 barrels of firewine and 1 barrel of oil in the crypt. Out of all of the fights, the big one at the Camp post-Minthara was the most difficult for me with SH and PC. I recommend breaking ladders, closing doors, luring enemies, arrows of darkness, and the obvious - just roll a 20. All of the tools to win are available in game should you take the time to find/understand them. Sometimes, you may just have to push a Tiefling that called you a funny word into a pack of Githyanki to have the Gith use all of their scrolls before you ambush them during their return
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