Syncback SE and Syncback Pro
have a "fast copy" mode designed for slow networks, where a database is used to track changes in local folders rather than re-scanning and comparing the remote folder each time. Very capable programs, if perhaps a little pricey for what they do (I wouldn't recommend the older and feature-limited freeware version).
You could also check out FreeFileSync
, which scans source and destination folders bafflingly quickly, but with (so far) 100% reliability in my experience. It's a fairly new project and the documentation's still a bit lacking (just a readme.txt file in the installation folder detailing the advanced options), but it's far and away the best free syncing utility I've come across to date.