I think this deal is a high but ultimately reasonable cost to create (hopefully) stability in goal. I wasn't a fan of bringing in Markstrom, but I see the point.
What I like about Fitz is his flexibility. He clearly was counting on Bahl to grow into the big defensive stopper this team needs. But, Fitz recognized that the more urgent and unique need was goaltending. Fitz probably would prefer not to have traded Bahl (similar to how he probably didn't want to get rid of Zetterlund). But, players like Bahl and Zetterlund are more available via trades, waivers, or free agency than someone like Markstrom. Rather than stick to his plan, he adjusted to reality and let go of players he wanted in favor of a player he felt the team needed.
So, yes, I think this deal temporarily filled one hole a goal while creating another hole in the lineup on D. But, I also think Fitz has a clear understanding of this and will look to resolve the problem.
Of course, finding the right solution is easier said than done. And Markstrom is 34 with only two years left on his deal. Fitz signed up for this problem. The clock is ticking.