I don't want to speak for David Finch, but here is a pretty popular example of Neal Adams using tangents to create a face of Deadman. I think it's important to understand rules are not there as hard never break things, they are there to help people self-correct their own work. In this case how do you avoid making your page look flat. As far as your page, yes and no. The tangent doesn't bother the flow but the first panel doesn't establish a solid environment so it looks a bit like a floating object with no dimension. The second panel I understand it's zooming into the mouth but it might be framed too tightly for others to read instantly. Most honest feedback I can give.