18% in a high end joint like the OP ate at is more than enough.
Especially when the "auto grat"is inclusive of the tax-which is just plain wrong.
I really hate this,and also being expected to tip 15-18% on an expensive bottle of wine on top of this.

I appriciate and support the working men and women of the food industry-since I have done this myself.
But there has to be a limit-and it looks like the place in the op is really testing that limit.