I am not sure Storj offers sender/destination anonymity (I would love to be corrected here). Also, I think the centralization aspect is with things like their metadisk product, not sure about the core network. I personally am a bit disappointed especially with the metadisk central server thing, but I fear bringing it up again because of the embarrassing politicking done by members of this forum at Storj - THERE IS NO CLOUD: it’s just someone else’s computer.
To the point, the HTTPS does seem a bit nutty. So the receiving user acts as a server performing diffie hellman with some agreed upon x509 cert? (Or is it centralized like metadisk and I just misunderstand thinking it is P2P?) Using a CA-based trust protocol like HTTPS makes it difficult to trust the sender when the CA concept is removed.