You are basically criticizing him because he used a word that has also strong human-centric connotations (as in "deliberate will," "free will," etc.). Sure, he could stay with causality only (i.e. "principle of sufficient reason") which would include all phenomena equally, but "causality" as a term does not denote change per se, only relationship. On the other hand, "will" (or that shamanic "intent" I've mentioned) automatically implies activity, which, I assume, was what he tried to communicate. All in all, and taking all flaws and insufficiencies of languages into account, I'd say that "blind will", exactly as e.g. "deafening silence", while both oxymoronic, express what they aim to express pretty well.

And once again, he compares physical inertia with instincts and biological drives of living things, not their will in the meaning of deliberate choices and motivations. Furthermore, and as I've also already said, he's pretty explicit about it, which simply can’t be denied.