I already won 2 cups without tanking, and other managers also done it.

Tanking does not make the draw of cup easyer, that only can happen If the SP are not assined until the start of New season.
So If you Tank and assigne the SP you have a normal draw.

2 seasons ago i tanked one of my teams, because it was not competitive anymore and was getting bad results, last season i became second, this season i am level 4 and i am playing a level 6 cup. So this is the prove that tanking does not make the cup easyer, only If you do not assigne SP that could happen.