Today I played against a weird 4-3-3 formation. He used:
st-st-st
mc-mc-mr
dl-dc-dc-dr
His quality is about the same as mine and with this formation he beats every formation in my league. Maybe he's switching to other tactics as the game starts i don't know. I played 4-4-2 with passing trough flanks but I lost 2-1. He also had much more shots on goal then I had so it wasn't luck.