Seem to have Hit a Brick Wall

You obviously spent a lot of time on the game, but you made the mistake of sticking with the characters you had at the beginning rather than thinking about what you want/should have toward the end. What everyone else said is a function of that first problem.

Eventually you'll have to find a squad that is designed to work well together. Others have posted good squads so I won't reiterate. Keep in mind this is a longer-term goal and yes it will take some time. Don't get discouraged and stay focused. I'm active on the forums so PM me if you have any specific questions and I'll try to help