Why not use a realistic formation that isn't broken then... The reason why it's rubbish in defence is because it's an awful formation. Just the game engine can't handle 3 strikers. If you only want to win without a challenge then go ah...
Yeah 3 strikers is known to be broken, some people argue it's not but they are the ones who refuse to use any other tactic on any save (because they know they suck when they don't use it)
If you want to be defensively sound then how about try not exploiting the match engine's weakness (3 strikers) and use a real formation.
But you use OP 3 strikers?