Ok so there is an issue with the MSQ bottleneck. The devs know that. The players know that. Everyone knows that.
Yes it was a large oversight to gate the rest of the expansion content through an instanced solo fight. Yes it is blocking you from enjoying the game during the early access period. We get that.
Going on and on about it and raging at people, arguing against the people that are defending the devs, generally polluting the air with negativity really isn't helping the situation. You aren't going to get passed this roadblock any faster by bitching about it. The devs are doing what they can to improve the situation.
Now that I have covered all of that rubbish...
My understanding of the reasoning behind not applying quick temp-fixes such as the ability to skip over the battle, or to reduce mob HP in the instance fight, and all of those quick adjustments they could do is due to the fact that none of these so called "fixes" alleviates the congestion in the slightest.
Just because the Raubahn instance is congested, doesn't mean skipping it would improve the situation. Skipping it or speeding up the instance will only push the congestion back to the next instance, and then what do they do? Reduce the mob HP or allow the next instance to be skippable?
Trickling people through is really the only solution to improve congestion. Think of a traffic jam. If they added another lane on a highway to improve congestion, all that does is widen the road. There are still the same number of cars on the road. What happens then, when the lanes go back down to two? (In this case, an instance).. Yes, again, more congestion occurs.
The only long-term solution is to gate the traffic by limiting the number of people to get through, which in-turn, thins out the traffic on the other side of the roadblock, which causes a much smoother journey for the rest of it.
The only improvement they can make at this point going forward is to add a queue system so people don't have to keep spamming the NPC. Hard-code a "line" like what we have been seeing people do on many servers, that allows people to go on with other content while they wait, and removes the randomness of someone getting in from 5 mins of NPC spamming and another spamming for 10 hours. So adding a DF style queue to solo content would effectively solve the issue.
I am not a programmer, nor have any knowledge on game development, however I presume a system like this would take more time than a quick 30 min job, sitting in the dev office.
For all you know, their "fix" is exactly this, and the comment that it will take several days to alleviate the issue, could be for this very reason.
So I want to end this post on this note -
Everyone is well aware of the issues, and they are doing what they can. Yes it is sucky, and yes it was a large mistake on the development side of things to not properly prepare for such a large number of people to try and queue into these instances. However the situation is what it is, and bitching about it further doesn't solve anything but create angst.
If it is really getting to you, log out. Do other things with your day. Come back in a couple of days, and enjoy the rest of the expansion when this situation is alleviated.