It seems you've never had to draw an entire comic page before whereas I have had to do both and I promise you that drawing a comic demands more from you than constructing a story. When you describe writing as...
...I really hope you're being hyperbolic because writing should not feel like this. No art or creation should feel like this. Yes it should be challenging but never painful or "excruciatingly hard".
What you're describing here is bad technique. If someone writes the outline for a story and then they find one plot hole (significant or otherwise) that sends the "whole project down the drain" that means their technique is flawed and that led to them writing such a fragile narrative that it could be ruined by the discovery of a single plot hole.
Having said that, I don't want to take away from the immense hard work that a lot of dedicated writers put into their work. It is a tough craft and demands just as much respect as any other but when we're talking about making a comic it is always the illustrator who will be dedicating the most time to the work but I don't think that's equivalent to the amount of value a creative brings. I think the value that a writer brings to a project is equal to the value an illustrator brings but the two creatives operate differently and the illustrator almost always ends up investing more time in the work.
Let's say you took 60 hours to construct a 60 page narrative for a comic; doesn't have to be a script.You spend each hour meticulously crafting one page at a time until you reached 60 pages. You figured out everything that would happen on all of those pages. You worked very hard on it as a writer. An artist would then have to work 10 times longer to convert your sixty pages of synopsis, outlines, storyboards, dialogue and character designs into cohesive sequential art.No matter how you look at it the artist always has to invest more time, they are always more challenged by the work. That's just how I see it.
Edit:
I'll read any replies but I won't say anymore about it. I don't want to go on and on.