If the database is large enough that you need multi-process backup, I'd suggest looking at pgbackrest- http://www.pgbackrest.org.
pgbackrest has parallel backup, incremental/differential/full backup support, supports compression, CRC checking, and a whole ton of other good stuff.
Increments in pgbackrest are done on file level which is not really efficient. We have done parallelism, compression and page-level increments (9.3+) in barman fork [1], but unfortunately guys from 2ndquadrant-it don’t hurry to work on it.
And actually it would be much better to do a good backup and recovery manager part of the core postgres.
