Minor spoilers follow for one of the main quest paths early on.

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After following the decursed botchling and notifying the Red Baron about his daughters whereabouts the quests has two objectives, go visit the daughter and keep looking for the missing wife. However the wife quests says you need to keep with your investigations in Velen. There are no direct leads to continue with the search. Am I right in assuming that you need to continue doing the other parts of the main quest namely find the witch branch?

Just want to make sure I am not missing something and can postpone that for a bit.

You're 100% correct. I did those quests in the opposite order as you and can confirm.

@nophilip: Thank you!

If you read the quest description it actually hints at where to look, but you are also correct in that doing the witch line will also allow you to continue it.