This for example was a winning deck for the Banshee on highest tower level. It was quite easy. Starting deck was the Rust Bucket (or how it is called). It would have been even easier with the shield maiden.
Well no wonder, that's simply a really strong and efficient deck! :)
But I agree that this archetype is a bit too easy to build for the power output it has. I'm not 100% sure to nerf Force Multiplier just yet. The card is pretty hard to balance because it has a hard cut-off between doing nothing and doing something very powerful. And you managed to upgrade your weapons to a point where you meet the threshold very consistently.
I was already planning to nerf the Lance, because it currently scales just too well with upgrades and the diagonal attack option is a crazy powerful effect already. And it seems it was your main damage source in this case.
This is amazing feedback, thank you so much!