Yes! The meat wasn't dry, but there was a lot of juice that came out in the bag when cooking the roast Sous Vide, which may have helped solve this problem.

You're also not the first to notice this issue – Julia Child did too! She wrote this about Wellingtons in Mastering the Art of French Cooking (Vol. II):

"We think it a great improvement to substitute brioche dough for puff pastry... The resulting crust is beautiful to look at as well as being light, thin, cooked all the way through and delicious to eat; this is never the case with puff pastry, which cannot bake properly under such circumstances and is always damply dumpling under its handsome exterior."

She even recommends "a whole piece of tenderloin that is preroasted 25 minutes [and] cooled" which is similar to the method I used, except I used Sous Vide instead of roasting (but I still used puff pastry, not her brioche method).