How to get Safari to accept Untrusted Certs on iOS8? (like Chrome)
This looks more like a SSL negotiation error; I suspect this is a settings issue, not so much a certificate issue;


an incorrectly configured proxy (possibly on the shared connection or even on the phone) 
a mismatched SSL/TLS setting (e.g. SSL version) 
the server failing the negotiation give a possible NAT or IP range issue with the phone (shared link with the Mac)


A Wireshark trace could help diagnose the differences between the Chrome and Safari connections. 

First attempt to rule out the shared link and get the phone on to the same corporate network as the host. Failing that, reset the Safari settings on the phone.