I've been going with a tank, archer and support (being a 2-handed sword wielding DPS Qunari) and i switch out the characters based on the objectives i've set out to do.
side note: would anyone else agree that really there should be 4 main classes instead of 3 seeing as you have a 4 man team? i'm constantly finding overlap (thus the above team structure of 2 warriors). I cant help but feel the game needed a pet to be the 4th character in some way
No, I've always liked that there are 3 classes because it gives you more flexibility. You can have each class represented and still be free to choose whichever fourth character you want. If there were 4 classes you'd never be able to take the characters that are the same class as you, thus missing out on their dialogue and banter.
Being able to take two of the same class means you aren't as limited in your selection. For example, you can actually take Iron Bull (being a two handed DPS type) and still have Blackwall or Cassandra tank without having to be short a mage or rogue. Just because two characters are the same class doesn't mean they fill the same role and being able to take two of a given class is a luxury I wouldn't want to lose.
I am actually playing the game in this way but sometimes it just makes me feel like something was less on the table.
I keep getting in this situation with 2 warriors (me and blackwall for example) where we're in the way of each other and the AI isnt smart enough to flank or move around so it can get a clean hit. could totally be an issue with the landscape but I feel like the further I get in, the more often it happens.
either way, totally fair point.