Disclaimer: I've already completed the game, so I know what to expect in the final mission.
That said, the fight right at the end was (almost) a complete balls-up. I managed to
kill the first 2 avatars, but then I got pinned down in the open area after the bridge by the constant waves of reinforcements. In the end I took the last avatar down after exhausting all my grenades and with everyone in the squad wounded.
And that was just on Rookie.
So, I'm wondering what the best approach is for that fight, for my second playthrough on Veteran. Should I charge in and try to eliminate each boss as fast as possible, or draw them out on to the bridge? What squad composition would people recommend?