Re: [No spoilers] Do I need a Mage in my DAI party?

Speaking only from memory on this one, and someone may be more rememberable on specific quests, but there are only a handful of them that would even "require" a mage to be in the party past the ones you listed. The main reasons are choices and dialogue.

For example (Without Spoilers Given) - In Hushed Whispers - This one has some choices, and based on who is in your party, dialogue, friendships and all that may change. I love story games and definitely want to experience it my own way, but speaking from experience, on some missions you have to be careful on depending on your own playstyle for story purposes.