RMAN Proxy Copy for better dedupe?

Our RMAN dedupe rates are pretty pitiful. We are seeing rates of 57% on full backups of databases that only append small amounts of data relative to their size - the DB is 1TB, but we are only adding 5 GB to the size each week.

I have seen that the proxy copy method will help with this, but it seems sketchy to me to say the least. I know very little about Oracle, but I need to help work with the DBAs on changing this if it will indeed fix this dedupe issue.

Needless to say, this is only one problem we seem to be having with RMAN, it has been very difficult to implement on any sort of consistent basis - is this true across the board?

Thanks,

DT