My most recent ink purchase was Dominant Industry's Earl Grey Tea, and it's a beautiful orange shade that is well-behaved (albeit not quite as red as I was expecting when I ordered it). Absolutely no complaints - I even love the bottle, however I will probably get through it slowly because I don't often use colours that are bright and eye-catching.
By contrast, one of the inks that is in my permanent rotation and I plan to continue purchasing over and over is Diamine Saddle Brown. It's a more subtle, darker brown that can pass for 'serious' writing but still has a personality that I prefer over many other browns. If the orange of Earl Grey is a cozy Autumn fire, Saddle Brown is the tree branches holding on to their last leaves and the damp earth underfoot on a cold, foggy morning - both enticing in different ways.
I do expect that you would need a medium or wider nib in order to get a real sense of shading out of the ink.
To your other concern, though, if anything I've found that Saddle Brown goes much darker when used in an F/EF nib. Certainly not to the point of being black, but dark enough that unless you were actually paying attention to the shade it doesn't immediately grab attention as being non-standard; to some people that defeats the point, but I find that sometimes (e.g. at work) I want to fly under the radar a bit while also knowing that I'm using 'my' colour.
It also looks amazing in notebooks that have a slightly ivory/off-white cast to the pages, where the overall sepia effect is something I really enjoy.