Bonded network interfaces normally show unbalanced throughput
This is expected for LACP bonds. LACP does not load balance on the packet level but does so on the connection level.
To get more throughput through an LACP bonded network interface, you will want to use multiple IP connections.
Note that a 1GbE network interface is capable of ~1.2Gigabytes/sec of throughput.
Additional details can be found at this link: