I agree that the signal-to-noise ratio in philosophy is very low. (I also strongly agree with the rest of your comment.) But let's be fair: it was philosophy that produced
1. Formal logic 2. Occam's razor 3. Scientific method 4. Church-Turing thesis
2. Yeah, William of Ockham was a philosopher. Score one for philosophy.
3. It looks to me as if almost everything important in the history of the scientific method is down to scientists rather than philosophers -- though, since the word "scientist" wasn't coined until the 19th century and disciplinary boundaries used to be more porous than they are now, they were often called "natural philosophers" and often did a certain amount of what-we-now-call-philosophy as well as what-we-now-call-science.
Francis Bacon is the usual chief suspect for introducing something close to the modern scientific method. He was an experimental scientist as well as a philosopher (though, it seems, not a particularly good one). Galileo was a scientist. Newton was a scientist. I suppose you might want to go back to Aristotle (though I wouldn't) -- but, actually, Aristotle was trying to do science as well as philosophy.
4. Since both Church and Turing were both trained and employed as mathematicians, it seems rather strange to credit the Church-Turing thesis to philosophy. (So far as I can tell, all the other important people in its history -- Goedel, Kleene, Post, Rosser, etc. -- were mathematicians too.)
You might consider these topics philosophical by definition. If so, the conclusion would seem to be that even philosophy is often best done by scientists and mathematicians, which doesn't speak well for philosophy as a discipline.
Leibniz was top notch in many, many things. Philosophy, math, linguist, lawyer, diplomat, engineer, psychology and sociology... lots of things. He was as particularly bad way to start your list which is supposed to support an argument that it was mathematicians who developed formal logic, since he shatters entirely the distinction you are trying to draw upon.
I think you have misunderstood my argument, which was not that formal logic was developed only by mathematicians with no philosophers involved (that would be nuts) but that saying it was done by philosophers as opposed to anyone else is quite wrong. And that argument would go through just the same even if we classified Leibniz exclusively as a philosopher (which would be just as wrong as classifying him exclusively as a mathematician; my apologies, by the way, for being sloppy about that).
I have to admit I can't imagine how what I wrote turned (on its way into your mind) into an attempt to draw a sharp dichotomous distinction between mathematicians and philosophers, but evidently it did and I'm sorry that I evidently wasn't clear enough. Yes, people can be both mathematicians and philosophers, or both scientists and philosophers, or all three; yes, the boundaries are fuzzy sometimes; it was no part of my intention to imply otherwise.