Why must the Borg have no single voice controlling their actions? Isn't that the idea behind a hive mind, that they all speak with a single voice, following a singular course of action? What's so bad about the storytelling device of giving that voice to a single actor to give it menace for the audience to identify with?
Right. Hearing the Collective speak through the Queen is no different from hearing it speak through the chorus of voices introduced in "Q Who." It's the same consciousness speaking in both cases; only the manner in which we hear it differs.
If there was no difference, the Queen wouldn't have been introduced by the aforementioned corporate bean counters. The fact is that most people don't intellectualize this far. They DO see the Queen as a personalization of the impersonal Borg, and as an individual. I agree with a great deal of your explanation of what we should be thinking is actually happening in front of our eyes (although, as stated by another poster, the Queen could be an emergent interloper or an alien interloper); but most moviegoers and tv watchers won't keep the concept of the Queen as focal node front and center in their minds as they watch. They will react to the Queen as an individual, however erroneous this perception and reception might be.
Short version: the vocal chorus is super-creepy and frightening in its multiplicity and in how it dramatizes the terrifying subjugation of individualism that is the core of Borgdom. The Queen, with her normal voice and single humanoid shape, comes across as another ho-hum villain (to me, anyway) compared to the vocal-chorus-as-Borg, no matter how I think of her.
Yes, this pretty much describes my position.
What people find scary is an individual deal. There is no right or wrong. As a general remark, it makes no sense to argue about which is scarier among several scary alternatives.