That splotch looks like it was made with watercolor paint on a coarse, open weave paper or watercolor block which will absorb all the water first and that sponging action will pull the pigment towards the edges as it dries.
When I think of "ink" from a fountain pen, I think black opaque or a nearly opaque liquid.
I don't know... Sorry, I might be the only one who doesn't think the ink blot you've created works that well.
I guess it all depends on what paper is used as to how the pigments travel while drying. Good fountain pen paper will absorb ink quickly to prevent smearing. For me personally, when I think of fountain pen ink, I think of a rainbow of colors. That is my draw to a fountain pen - because of the variety of colors you can get. Right now, I have orange ink on one of my pens.
Anyway, I know that not all logos appeal to all people. There's a saying, "You can please all people some of the time, you can please some of the people all of the time, but you can't please all of the people all of the time."
I guess to me, the most important thing is if the customer is happy, second is if I'm happy, and third is if other people are happy.