What specializations and multi spec to use for each unique character without breaking the game?

I have mostly gone through my playthrough as leaving people who they are at start and keeping Hawke as a gunslinger focus but I feel like I probably played a very basic experience despite winning as no one even got downed once except on the jedi introduction mission where she died twice due to her deflect being random. Also found sharpshooter disappointing with a long gun.

So what are the pros and cons of each for the companions?

I actually looked across top posts but there were none.