No; miners have a natural incentive to want to be closely connected to as many other miners as possible (to reduce orphan costs).

RE: Evaluating sybil resistance: I would still like to see blocks and transactions being broadcast over another completely different networking protocol, either peer-to-peer or not. More diversity so we're not relying on the one p2p network would be great, and, depending on how it was implemented, might automatically bring sybil resistance.