The easy way is to take like 20 bear trap you can find in the forest and put them ALL in the same place in the center of the eggs then you can kill the babies to bring the mom and run behind the trap, it should one shot her as they make alot of damage. You can loot back your traps and do the same to the second queen. It can be called cheating, but a this level in darkness mode it's unfair how powerfull they are so you have to use tricks to stay alive.

You didn't watch the video, Mugiwarah, isn't it? It takes Geralt 20 seconds to kill the Endrega-Queen - on dark. I would have been very disappointed if the fight would be shorter.

Your solution is no cheat: You've found a useful application for the traps. But your solution isn't easy, but laborious.

It's more because of Geralt movement ont The Witcher 2, the same fight with The Witcher 3 would be easier as animation and fight movement are better on the third game, but with the slow Geralt of Witcher 2, all fight are harder.

I did the stacked traps thing to kill one of the endrega queens that kept massacring me. The forest around Flotsam was quite life-threatening. By Chapter 2, with more points in the skill trees and different enemies, Geralt felt a lot less vulnerable.

Sorry I did not give you this info earlier (had to find my notes).
The Alchemy talent tree has 2 uses for any type of build.
1) Put 6 points in and get 2 levels of Impregnate to increase the effectiveness of Mutagens.
2) Put another 6 points in to get 5 Mutagen slots.

I am a min/max type player. As such I would not put any Mutagens in a slot until I had learned 2 levels of Impregnate.
Also, I only put in Greater Mutagens, unless I was lucky enough to get a Madness Mutagen. (N.B. Basic Madness Mutagens are the only type available).

I farmed: Engrega, Nekkers, and Drowners for Greater Mutagens early in the chapter and did not complete the Engrega or Nekker Contracts until I was "done framing" toward the end of the chapter.

I Chapter 2 I farmed Harpies for Greater Mutagens.

Not just yet. Keep playing and you will eventually see something happening there. ;)

Oh ok, have I tried to do something before I was supposed to? :-)

Hmm ... something odd came up in the Kayran:Ostmurk quest. It seemed I was able to make the Mongoose potion without the Ostmurk (although I have since found it in the cave behind the waterfall). I assume that must be a bug? If so, it's a bit sloppy, as it seems to relate to the main quest. Hard to see how they could have missed that during playtesting.

Please don't post any spoilers about the Kayran, as I haven't tried taking it on yet.

(btw, I have now taken out the Endrega Queens. It's funny, with a bit more development, better gear, use of snares/traps/Yrden, they seemed almost trivial)

Finding and using the ostmurk is optional. According to the wiki:

[The mongoose potion] can be made with ostmurk or any other alchemy ingredients that contain fulgur such as endrega embryo.

And:

If you make a Mongoose potion with some other ingredient [other than ostmurk], the quest [The Kayran: Ostmurk] will still not update.

Ok, thanks for the info. It didn't seem very clear that quest was optional though. The way I interpreted it was that the ostmurk was some super-rare ingredient that was required to make the potion. It also seems a bit odd that the quest doesn't resolve either when you make the potion without it or find the ostmurk. Oh well ...

Sorry, one more question: so, do I have to fight the kayran with Sile, or is there a choice there? One of the quest prompts says: 'Find the ostmurk or go with Sile to fight the kayran', which makes it sound as if there is a choice. However, I don't see any obvious way to take it on without her. If fighting without her is possible, does that choice have much effect on the plot?

No, there's no choice.

This isn't precise enough. Should have been: "Find the ostmurk first or go with Sile directly to fight the Kayran."

My advice: Prepare the potion first, let Geralt consume it before the fight. It doesn't really help to beat the Kayran, but Geralt gets partial resistance (permanent) against poisons ....

Ok, thanks! Yeah, to me this ostmurk thing comes across as very sloppy design. The way it is so unclearly explained and coupled with the fact that the quests don't resolve properly, even when you do find it. It's a bit disappointing that CDPR would not have patched it at some point, given how obvious it is and how easy it should be to fix (we're talking a few lines of text and some quest scripting).

I mean, overall I'm enjoying the game, but the ostmurk quest is a real mess.

If i remeber correctly, you can use any ressource that are the same group than the ostmurk to craft it, you don't need it to beat the boss, but it's +20 000 (once again i don't remeber the exact number) poison resistance can help you against him in higher difficulty. Like said before, drinking the potion give you a permanent bonus even if you dont drink right before the fight.