Honestly though, don't get discouraged
Philosophy is one of the most competitive fields, and it's STUPER hard to get in a PhD program
My friend who has high GRE scores, a 4.0, great letters of rec, grad conference experience, Grad research assistantships, etc etc got like a million rejections, 2 waitlists, and only 1 offer
I myself got shut out of 11 schools last year
It's almost unfathomable!
But I still think that if you persist, you will eventually succeed
As for your writing sample-- I was told by a prof in the department to which I am applying this year that they do not look at the WS so much in terms of content, but in terms of *methodology* to see whether you possess the SKILLS necessary to do good philosophical work at the doctoral level
That being said, it seems a bit contradictory to attempt to separate the two, but I think the key is to remember that (historically speaking) Philosophy was characterized not entirely by a common set of problems, but by a methodology of inquiry. You can be Leibniz and write about something stupid and ridiculous like MONADS, but the content of your paper will not matter so much if your ARGUMENTATION is rigorous and sophisticated--in a word "philosophical"
Does that make sense?
So while it definitely would be ideal to present a WS of which you feel 100% confident, I wouldn't necessarily kill myself over the content, but rather make sure that the more *formal* aspects of the paper are impressive
Good Luck