Is there a point in continuing to test the traditional SPAMCOP_NET RBL?
Yes, the RBL checks Received: headers IP addresses, SURBL checks domain names in URLS. They are *completely* different things, they just happen to use the spamcop reporting system as a source of spam reports to build databases from.
Is this now redundant?
No, see above.
Does setting the score for RCVD_IN_BL_SPAMCOP_NET to 0 prevent the DNS lookup?
Yes
or simply invalidate the info received. (my goal is to speed up spamd)
No, it disables it.
As I add more SURBL's, are there generally matching rules which should be canceled out (bigevil being an example)?
sa-blacklist-uri and big/midevil are almost completely superceded by ws.surbl.org. All the other SURBLS are AFAIK unrelated.
