In my rogue playthrough, I was scouting alone through the underdark and came across the kuo-toa. My rogue solo'd them.
In my fight with Gut, my rogue killed Gut while locked in the room with her while my party took out the other goblins outside the door.
I'm currently playing a beast master ranger, using a raven as a companion. I didn't do any prep work on the spiders. I just rushed in, started the fight and won. I didn't bother breaking the eggs; I fought the little spiders also. My raven companion and Wyll's imp did most of the work with the small spiders.
With the hag, I discovered the fireplace passage. That made her go hostile and attack me. Without landing a single critical, I beat her before she escaped to where she keeps Mayrina prisoner.
I'm not using barrels. I haven't dipped once. I haven't used a single specialty arrow.
Shrug. I get that other people are having problems, but I'm just not seeing it. For what it's worth, I'm really enjoying the combat, and I think it's interesting maneuvering through the terrain.