Every lineup I use got at least:
Imho it's optimal. I start with a tank. Later in battle, if there are many enemy aircraft I can spawn in fighter/AAA (depends on map and cap situation).
If there are no enemy aircraft and no deadly AAA, attacker will be great to clean some defense points (city maps and places where enemies got 2-3 tanks in one place).
Long story short, having such lineup give a really nice room for maneuver.