Edit: Maybe most of the following text should be in spoilers? Although I think people reading in this story subforum would expect everything being a spoiler. Anyway, BEWARE!
I didn't want to bore you with my game problems, but as you made the mistake to ask

:
I don't like story driven games with the "do it again to succeed" principle in mind. For example I'm a sworn enemy of Souls games (if we allege there is a story). I always had suspicions against Larian in this field since I played D:OS 2. In the Isobel fight there are in my opinion some very unfair design decisions which go in the said direction.
Firstly, you don't get the slightest hint that an important fight is possible in the save haven of the inn area. First time of the fight I was more or less depleted of spells etc. because I spoke to the NPCs before long resting. Jaheira directly hints to Isobel, so I went and spoke to her, no chance to deal with the fight. Ok, you could say that you have to be ready every time.
Secondly, I really don't like the win/fail conditions of the fight. The next trial of course I was prepared (and I hated to do it again, knowing what would happen). I managed to kill Marcus first turn with just my main char (hasted ranged Fighter + a bit of luck) before he could do much harm to Isobel. But the next turn the winged mobs came in and the abduction sequence was started immediately, no way to do anything. The sequence btw is a lie, because the mob walks away with Isobel in it's arms unhindered as if there weren't a full party of experienced killers plus the inefficient friendly inn NPCs around. For me that is a very bad design.
Thirdly, can you accept the lost fight? I my opinion, not really. The inn is gone, you get a huge fight against the formerly friendly NPCs (why are they affected but not you? why Isobel didn't give them her blessing too but only you?) and as far as I know the Karlach quest line is over. That makes most people reload, I think. Also bad design for me personally, ususally I don't like to reload if I get negative results, but here ...?
I don't cry about difficult fights. Yesterday I met the fat golden Thorm. At the start of the battle 2 of my chars were down on the floor, the third had 20% hp, the last 30% hp. I thought, it's unfair that one mob can down two of my chars and take away most of the hp of the other two before I can even react. Then I thought that it was Tactitian and it's a boss mob and that I was careless not to explore before walking into the trap with the whole party. I took the challenge and won the fight after a long and desperate battle.
The Isobel fight is different, it's design is an unfair crap in my opinion because you cannot react and plan according to the events. You have to know it and get lucky or not. Third trial I put difficulty to "easy" and won the fight but a bad feeling remains. I'm sure I would have lost the first trial of the fight on "easy" too.