what if a game have very different results depending on the mode the player use.

Example: Total War: Shogun 2.

In this game, the campaign map should get 0%-25% and grade D. But when playing battles, the game should get maybe 60%-80% and grade B.
Playing in solo means mainly use campaign mode, meaning mainly campaign map + some battles, resulting on a poor or limited S3D experience.
But playing in multi-players plus occasional solo battles will result on a good enough S3D experience.

I've to say that campaign and battles are two very different experience in term of gameplay.

Should we made two submissions for this kind of game?

Good question. I think a game should be rated totally, and not divided into modes. I don't think anyone would want a half-baked product, so GG3D should rate accordingly.

However, in the comments attached to the game, I would encourage sharing the positive/negative experiences and conditions for those experiences even if the final rating works out differently.

Regards,
Neil