I'm not the best writer, but it is a strength. I might be a 90th percentile writer.  And I'm not the best marketer, but it is a strength. Again, maybe 90th percentile? I'm better than most, but if you pass 100 people on the street it won't be hard to find some people better

Great points. 
It's beautiful that I can relate to everything you have said here. My shortcoming when it comes to writing is editing. 

I am not the best editor; It's always too difficult for me. However, when I do it, I do it well. 

So maybe 90th percentile.