Bitter harvest is easy if you move towards the spawn point and fight the monsters there. They then only concentrate on you. Do it when you a couple of levels higher or when you got the right oil and things will go much smoother.
Extreme cosplay is a real PITA. One of the problems is if you come across it but don't start it and travel away it goes away for good. So you are always forced to do it then and there no matter what. So be fully rested with full supplies of potions etc before going near the quest marker. And then you have to kill the fire guys ASAP. Here is one quest where it's much better to change your armor to get a high resistance against weapons (non-witcher gear) as they will beat on you while you try to kill the fire mages.
For the escort are you referring to For Fame and Glory outside of Larvik? If so just sprint into the cave first and the monsters focus just on you. Or is this some other quest?
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