>A global passive adversary is the most commonly assumed threat when analyzing theoretical anonymity designs. But like all practical low-latency systems, Tor does not protect against such a strong adversary. Instead, we assume an adversary who can observe some fraction of network traffic; who can generate, modify, delete, or delay traffic; who can operate onion routers of his own; and who can compromise some fraction of the onion routers.
From what I understand, connecting to an onion address 'just' involves 6 routers, not the typical 3. (Of course an oversimplification.)
Or am I misunderstanding your threat model here?